Cost benefit analysis of the proposed national surgical

Cost benefit analysis of the proposed national surgical site infection surveillance and response programme

Martin Hefford, Melleny Black, Sally Wyatt 12 May 2011

Surgical site infection surveillance CBA i

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Acknowledgements

We acknowledge the kind assistance of a number of individuals and groups who provided information in support of this report, including: the reference librarian at the MoH, DHB infection control staff, Southern Cross quality unit staff, the Infection Control Division of NZNO, ICNET, RL Solutions, ACC treatment claims unit staff, and the ad hoc clinical advisory group.

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Surgical site infection surveillance CBA ii

1 Executive Summary

1.1 Context & Purpose

Surgical site infections (SSIs) are a major burden on patients and on health sector resources. SSIs are the second most common form of hospital acquired infection (after catheter associated urinary tract infections). SSIs are costly to treat, are associated with increased mortality and have an impact on quality of life. New Zealand currently has no national programme to monitor and help reduce the rate of these infections.

In 2010 the National Quality Improvement Programme (NQIP) Infection Prevention and Control workstream recommended implementation of a systematic national surgical site infection surveillance programme. The objective of the proposed programme is to facilitate comparisons between providers and to motivate and support teams to reduce rates of surgical site infections by implementing evidence-based changes to surgical practice. The Health Quality and Safety Commission (HQSC) is now considering the recommendation, but wishes to understand the likely costs and benefits of the programme before deciding whether or not to invest in it.

This study is intended to inform decision making by estimating: 1. The likely cost to the health sector of the proposed programme (one off and

recurrent); 2. The likely financial benefits to the health sector; and 3. The likely return on investment. The analysis presented in this report is primarily a financial cost benefit analysis (CBA) from the perspective of the health system funder, as opposed to an economic CBA from a societal perspective. The two types of analysis differ in that a financial CBA does not incorporate the wider benefits to the community from infection surveillance, such as improvements to quality and length of life, the avoided costs to patients and reduced time away from work.

1.2 The cost of an SSI surveillance programme

The proposed surveillance programme would involve monitoring infection rates by collating data on infections that occur in patients who undergo various types of operation including hip and knee replacements, caesarean sections and coronary artery bypass grafts. The objective of the proposed programme is to facilitate comparisons between providers and to motivate and support teams to reduce rates of surgical site infections by implementing evidence based changes to surgical practice.

Surgical site infection surveillance CBA iii

The cost of the programme depends on whether an automated or manual data collation process is used. The major cost in the manual option is labour, and the major cost in the automated option is the cost of the information systems. The automated option is preferably from a data quality and overall utility perspective. The estimated cost of an automated programme is shown below. We note that considerable uncertainty remains around the cost of implementing a national clinical information system to support the surveillance programme.

Table 1: Summary programme modelled costs, automated option, low medium and high cost scenarios

Cost scenario Cost component

Low Medium High year 1

(capital) year 2 -10 year 1


(capital) year 2 -10

Local DHBs 2,223,200 228,800 2,779,000 286,000 3,928,500 343,200

Central agency 1,256,000 544,000 1,570,000 680,000 2,251,500 816,000

Total 3,479,200 772,800 4,349,000 966,000 6,180,000 1,159,200

The programme is expected to have the capability to respond to SSI rate issues and provide training and set standards, as well as to collate and interpret data; hence we have characterised it as a surveillance and response programme.

1.3 Current SSI rates

After reviewing data sent to use by DHBs, and international studies we applied the following estimates of the incidence of SSIs nationally, assuming that no post discharge survey will be used (which results in lower rate estimates). An implicit assumption is that the rates include approximately a 50/50 mix of superficial and deep/organ infections, except in the case of caesarean sections where the number of superficial infections is expected to be higher.

Table 2: Current SSI rates for selected procedures

Category

DHB data International data Modelled (case)

Caesarean section Mean (SD) 2.7 (1.7) 2.4 (1.2) 2.5 (medium)

range 1.4 - 4.7 1.2 - 5.0 1.2 (low) - 3.8 (high)

Hip/knee JR Mean (SD) 1.9 (1.0) 1.6 (0.7) 1.7 (medium)

range 1.1 - 3.8 0.7 - 3.1 0.9 (low) – 2.6 (high)

CABG Mean (SD) 4.00 3.1 (1.4) 3.1 (medium)

range na 0.7 - 4.5 1.7 (low) - 4.6 (high)

Surgical site infection surveillance CBA iv

Table 2: Current SSI rates for selected procedures

Category


Other SSI Mean (SD) 1.3 (0.7) 2.7 (0.9) 2.0 (medium)

range 0.3 - 1.7 1.6 - 3.8 1.0 (low) - 3.0 (high)

We found good evidence that surveillance programmes can reduce the rate of SSIs, and adopted the following expected reductions in the model.

Annual rate of reduction in surgical infections year one reduction

• Low: 4%

• Medium: 8%

• High: 12%

Maximum cumulative reduction over the ten year period (adjusting for start dates as applicable):

Table 3: Modelled maximum ten year cumulative reduction in SSI rates

low Medium high

Knees 30% 50% 70%

Hips 30% 50% 70%

CABG 30% 50% 70%

Caesareans 30% 50% 70%

Other 1 20% 35% 50%

other 2 10% 20% 30%

1.4 Savings from avoided SSIs

We estimated the cost savings for the health sector per SSI avoided from a combination of NZ and international data. The estimated annual numbers of SSIs avoided, and associated savings are shown below.

Table 4: Key savings estimate parameters

Knee JR Hip JR CABGs Caesars Other

Modelled saving per SSI (+/- 20%) $ 21,000 $ 21,000 $20,000 $4,500 $10,000

Modelled starting # SSIs/yr 62 74 107 377 400

Modelled end # SSIs/yr 30 37 53 188 290

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1.5 Cost benefit summary

The expected ten year costs and benefits are summarised below.

Table 5: Ten year estimated summary costs and benefits,automated scenario

Cost / benefit Medium scenario Credible range

Surveillance programme costs

One off costs $4.4 million $3.4 - $5.1 million

Annual cost $1 million $0.8 - $1.2 million

Cumulative ten year costs $15.8 million $12.5 - $20.3 million

Surveillance programme benefits

SSIs avoided (ten years) 1,678 473 – 3,641

SSI costs avoided - ten year savings $18.8 milion $4.4 - $49 million

SSI costs avoided – annual savings at year 10 $6.2 million $1.1 - $11 million

Bed days freed up 19,765 5,793 – 42,000

Deaths avoided (ten year total) 50 14 – 109

Using a discount rate of 3.5%, this gives a net present value of $0.94 million in the medium scenario – meaning that the health sector would be better off financially over the ten year period by investing in the surveillance programme. However, the picture varies considerably, from a worst case of negative $14 million, to a best case of positive $27 million

The most important variable affecting the financial NPV is the actual incidence of serious SSIs in NZ. Another important estimated value is the likely cost of implementing the required information systems.

We draw the following conclusions from this cost benefit analysis:

1. A national SSI Surveillance Programme is highly likely to lead to significant reductions in surgical site infection rates

The evidence for this conclusion is the experience internationally across a number of countries, the Southern Cross experience, and the reported changes in rate at DHBs when they have introduced surveillance of particular procedures. We calculate that a surveillance programme could plausibly avoid some 1,678 surgical site infections in its first ten years.

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2. The financial case for a surgical site surveillance programme is positive, but not under all scenarios

An automated SSI surveillance programme is likely to cost some $4.4 million to introduce, plus ongoing costs of some $1 million per annum to maintain. The medium (most likely) case gives a positive net present value of $0.9 million over ten years, using a discount rate of 3.5%. However, if the real incidence of serious SSIs is significantly lower than expected, then the NPV becomes negative - with a value of negative $6 million not unlikely.

3. Automated surveillance is likely to be superior to manual surveillance The automated option costs a similar amount to the manual option, and generates substantial spillover benefits in terms of ongoing costs savings and the ability to extend the programme to cover other procedures/infection types. However, this finding is very sensitive to estimates of the cost of the information systems. We suggest further work with DHBs and the NHIT board if a programme is to be introduced, as an automated system is likely to be beneficial in the long run, but manual data collation is better in the short to medium term.

4. An economic CBA is likely to be strongly positive Notwithstanding the conclusion that the NPV is only marginally positive, an economic CBA – including the cost of time off work and other societal costs - would be very likely to result in a strongly positive NPV in all reasonable scenarios.

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Table of Contents

1 Executive Summary .............................................................................................. ii 1.1 Context & Purpose ..................................................................................... ii 1.2 The cost of an SSI surveillance programme .............................................. ii 1.3 Current SSI rates ....................................................................................... iii 1.4 Savings from avoided SSIs ....................................................................... iv

1.5 Cost benefit summary ................................................................................ v

2 Introduction ........................................................................................................... 1

2.1 Surgical Site Infection surveillance in New Zealand ................................. 1

2.2 Programme intervention logic .................................................................... 2

2.3 Purpose ..................................................................................................... 3

2.4 Scope ........................................................................................................ 3

2.5 Approach ................................................................................................... 3

2.6 Structure of this paper ............................................................................... 4

3 Estimating the cost of the proposed programme ..............................................5

3.1 The proposed national surgical site infection surveillance programme .... 5

3.2 Sizing the capacity needed to deliver the programme nationally .............. 6

3.3 Sizing the capacity needed to deliver the programme locally ................. 10

3.4 Summary SSI programme costs ............................................................. 13

4 Estimating benefits from SSI surveillance ......................................................... 15

4.1 Issues in calculating benefits ................................................................... 15

4.2 What reduction in SSI rates might be achieved through a national programme? ............................................................................................ 17

4.3 Estimating the cost savings associated with a reduction in SSIs? .......... 23

4.4 Estimated benefits from SSI surveillance ................................................ 26

5 Is a national surveillance programme a worthwhile investment?.................. 28

5.1 Ten year costs and benefits .................................................................... 28

5.2 Estimating Net Present Value ................................................................. 29

5.3 Issues requiring resolution as part of the next stage of the project ......... 30

5.4 Limitations ............................................................................................... 31

5.5 Conclusions ............................................................................................. 31

Surgical site infection surveillance CBA viii

6 Appendix .............................................................................................................. 33

6.1 Indicative Surgical Site infection dataset to be provided by DHBs ......... 33

6.2 DHB reported SSI rates ........................................................................... 34

6.3 Southern Cross Hospitals Limited Surgical Site Infection Surveillance Programme .............................................................................................. 34

6.4 Literature review ...................................................................................... 35

7 References ........................................................................................................... 61

Surgical Site infection Surveillance CBA 1

2 Introduction

2.1 Surgical Site Infection surveillance in New Zealand

Surgical site infecti1ons (SSIs) are a major burden on patients and on health sector resources. SSIs are the second most common form of hospital acquired infection (after catheter associated urinary tract infections) and have been estimated to cost between $US3.45 billion and $US10 billion per annum in the USA1. In NZ the Auditor General estimated the cost to be some $140 million in 2003. SSIs also have an impact on quality of life and are associated with increased mortality2.

NZ currently has no national programme to monitor and help reduce the rate of these infections. Each DHB has their own approach to infection surveillance, making inter-DHB comparisons difficult. Surveillance programmes are in place in most comparable jurisdictions (Scotland, England, most states in Australia, USA, Canada, Germany, Netherlands, for instance). Implementation of a national surveillance programme in New Zealand has been seriously considered and examined by the Ministry of Health (MoH) since 1996. The rationale for a national surveillance programme is:

• to drive consistent measurement locally, leading to more accurate and timely feedback to local clinicians and hence to changes in practice resulting in reduced infection rates and better patient outcome;

• to benchmark between facilities leading to identification of high and low performers, with corresponding opportunities for those with high rates to learn from those with low rates;

• to measure the national burden of disease resulting from surgical site infection and thus to inform:

− decision making about what resources to allocate to reduce the burden of

disease; and

− Changes in infection rates over time.

A proposal to develop a national surgical site surveillance programme was circulated in draft by the National Quality Improvement Programme (NQIP) Infection Prevention and Control workstream in 2009, and generally favourable comments were received from a range of stakeholders. After considering feedback, the programme steering group recommended implementation of a systematic national surgical site infection surveillance programme. The objective of the proposed programme was to facilitate comparisons between providers and to motivate and


support teams to reduce rates of surgical site infections by implementing evidence based changes to surgical practice.

The Health Quality and Safety Commission (HQSC) is now considering the QIC workstream recommendation, but wishes to understand the likely costs and benefits of the programme before deciding whether or not to invest in it.

2.2 Programme intervention logic

The intervention logic for the proposed programme is summarised in figure 1 below.

Figure 1: SSI surveillance programme intervention logic

In effect the impact of surveillance is to shine a spotlight on SSI rates in general, and on providers with higher rates in particular. In order for the highlighted rates to be accepted as valid by clinicians and management, the rates need to be able to be risk adjusted using accepted practices – which requires collection of a specific dataset beyond what is captured for the current national data collections.

Inputs

•We invest in these activities:•National surveillance programme including national and local

capability

Outputs

•To deliver these outputs:• Standardised collation and reporting of SSIs•Regular reporting of risk adjusted SSI rates (benchmarking)•Advice on best practice response

Impacts

•To achieve these impacts:•Increased awareness of SSI rates•Increased use of best practice infection prevention strategies•Reduction of mean SSI rates•Reduction in variability between hospitals

Outcomes

•And these medium term outcomes•Reduced cost of treating SSIs•Reduced patient morbidity and mortality associated with SSIs


2.3 Purpose

The purpose of this study is to inform decision making on the proposed surveillance programme by estimating: 1. The likely cost to the health sector of the proposed programme (one off and

recurrent); 2. The likely financial benefits to the health sector; and 3. The likely return on investment. The return on investment (ROI) is measured using a 10 year net present value (NPV) calculation – which sums the cost of an investment, and its expected return over a period of time, and applies a discount rate to future cash flows in order to understand the discounted presented value of those flows.

2.4 Scope

The analysis presented is a financial cost benefit analysis (CBA) from the perspective of the health system funder, not an economic CBA from a social perspective. The two types of analysis differ in that a financial CBA does not incorporate the wider benefits to the community from infection surveillance, such as avoided costs to patients, increased quality and length of life, and reduced time away from work. Differences also exist in terms of the appropriate consideration of capital costs, and dead weight costs are excluded. We have noted the major non-financial benefits likely to result, but have not attempted to value them explicitly in economic terms. Should an economic analysis be required at a later point, a financial CBA is a good base from which to develop a model incorporating the wider economic picture.

We modelled costs and benefits specifically for the first two proposed tranches of surveillance (stage 1: hip prostheses, knee prostheses, stage 2: caesarean sections and coronary artery bypass grafts) and allowed for extension over time to another two tranches of unspecified elective procedures (other1 & other2).

2.5 Approach

The overall approach to estimating costs and benefits is summarised below.


Figure 2 Approach to estimating costs and benefits

2.6 Structure of this paper

This paper reports on the issues in the following sections:

• Part 1 summarises the report

• Part 2 describes the context and purpose

• Part 3 describes our estimate of costs and the evidence on which it is based

• Part 4 describes our estimate of benefits and the evidence on which it is based

• Part 5 gives a consolidated view of costs and benefits, and our conclusions

• The appendices provide additional supplementary material.

Estimate costs

Describe proposed national SSI surveillance programme

Discuss cost elements with key informants

Write to DHBs asking for cost estimates

Review costs from similar programmes elsewhere

Obtain vendor software cost estimate

Model likely quantum of national and local costs (including

sensitivity analysis)

Estimate benefits

Collate volume data for selected procedures

literature review to estimate current infection rates

Data gathering from DHBs to check NZ versus international

SSI rates

literature review to estimate marginal cost of infections per

procedure

literature review to estimate reduction in infection rates from

a surveillance programme

Model likely quantum of benefits (including sensitivity

analysis)

Estimate return on investment

Spread costs over ten years and generate NPV

Spread benefits over ten years and generate NPV

Calculate ROI (including sensitivity analysis)

Write up method and findings

Peer review

Finalise


3 Estimating the cost of the proposed programme

3.1 The proposed national surgical site infection surveillance programme

The proposal is that all DHBs undertake continuous monitoring of all elective procedures falling within certain agreed categories. DHBs would report both denominator (i.e. data on all funded procedures included in the programme) and numerator (i.e. details of relevant surgical site infections) data to a national programme coordination centre.

The national coordination centre would:

• promulgate standard definitions and case detection protocols

• collate results and report back risk adjusted rates to each DHB for each procedure.

• provide advice and support on best practice - probably using a collaborative methodology to assist DHBs to learn from each other and from best practice internationally

• have the following organisational competencies:

− biostatistician/epidemiology

− clinical microbiology/infectious diseases.

− programme management

− informatics / IS advice

− training & online resources

− ability to audit local programmes

• coordinate national promotional campaigns.

The first two proposed tranches for surveillance are:

− Stage 1: surveillance of elective hip and knee replacements

− Stage 2: surveillance of caesarean sections and coronary artery bypass

grafts.

Other procedures would be added over time in consultation with the sector.


Other relevant proposed programme parameters are:

• continuous surveillance of all selected procedures (including those performed at private hospitals with public funding) using US NHSN definitions

• identification of cases of SSI using microbiology, readmission and other relevant databases to flag patients with possible SSI (rather than manual scanning of notes).

• the NNIS risk index and other data is used to adjust for case mix between hospitals

• hospital databases are used to identify all patients that have been readmitted within 30 days of discharge (or within 1 year of discharge for procedures involving implants). Those that have had a relevant surgical procedure can then be identified and reviewed to determine whether the NHSN definition for SSI has been met.

• mailouts/surveys of patients to identify post discharge infections that do not result in readmission are not included

• DHBs are able to generate their own reports from submitted data

• the programme will incorporate information technology to reduce the labour-intensive aspects of surveillance.

• the programme meets the current New Zealand Standard for Infection Prevention and Control and is centrally coordinated with ongoing national oversight, governance and leadership

• an annual report for all DHBs is publically issued.

The indicative surgical site infection dataset developed by the NQIP working group is provided as appendix 1.

3.2 Sizing the capacity needed to deliver the programme nationally

We have estimated the capacity required to deliver the programme nationally. Our estimates are based on information received from VICNISS (the State of Victoria hospital infection surveillance and control programme), the Hand Hygiene NZ programme requirements, estimates from infection control international software vendors, advice from HIQ, which hosts the national InterRAI clinical information system, and advice from key informants.

Explicitly we assume that the central agency needs the ability not only to receive data, but also to analyse and interpret it; to provide training, to establish and audit against standards, to facilitate collaboration between DHBs and to run


communication / education campaigns. In effect, it is not just a surveillance programme; it is a surveillance and response programme.

3.2.1 Developing a national information system

Development and maintenance of the national information system is a major expense both for individual DHBs and for the central agency. We developed two estimates of the programme costs – one assuming implementation of a national information system to automate infection surveillance data collation and reporting (labelled ‘Automated’), and one assuming mainly manual processes (labelled ‘Manual’). The programme working party emphasised use of automated data integration and case detection methods wherever possible, but we are conscious that the cost effectiveness of an automated system will depend on the cost of implementing and running the system, and that national IT systems have a history of running behind time and over budget; therefore we considered it prudent to also estimate the cost of a manual option.

The Automated scenario is based on estimates provided by two international infection control software vendors: ICNET and RL Solutions. It assumes a centrally hosted national information system, with feeder connections to laboratory, theatre and patient administration systems in each DHB. The option of regional information systems was discussed with National Health IT Board staff, but their advice was that if a programme is to be implemented in the next 3 – 4 years, then a national solution is likely to be more cost effective. We also reviewed costs provided by HIQ – a subsidiary of Taranaki DHB - which hosts the national InterRAi clinical software system.

The reader should note the following points in relation to the information system cost estimates:

• Use of vendor cost estimates does not constitute agreement to use those systems or agreement to those costs.

• A competitive tender process may reduce costs substantially.

• A hybrid option - in which the central agency buys a standard software product and specifies the required inputs and definitions from DHBs, and then lets each DHB decide when and whether to switch from manual to automated collection – may also be a useful way of progressing a national surveillance system.

• The NHIT Board advises that DHBs IS programmes are already full with regional priorities, and an investment of this type will need to be signalled several years in advance, and given a clear mandate from central government.

• The cost of project management can vary significantly depending on the ability of central agencies and DHBs to reach decisions quickly and without relitigation.


3.2.2 Annual central agency costs

Our estimate of the annual cost of running the central agency functions (once established – i.e. excluding set up costs) is between $544,000 and 816,000 per annum – as set out below.

Table 6: Central agency capacity and annual cost estimates

Central agency expense estimates $ per year Automated Manual

Item Low Medium High Medium

Software licenses, hosting, website & database maintenance

264,000 330,000 396,000 80,000

Programme coordination & management 88,000 110,000 132,000 110,000

Data collation, analysis and reporting - to DHBs and public

72,000 90,000 108,000 90,000

DHB training & collaboration processes 16,000 20,000 24,000 20,000

Other direct costs - resource development & promulgation, travel, audit 24,000 30,000 36,000 30,000

Communication / education campaigns 16,000 20,000 24,000 30,000

Medical input / epidemiology/ expert group 24,000 30,000 36,000 40,000

Serviced office costs & corporate overheads 40,000 50,000 60,000 50,000

Total 544,000 680,000 816,000 450,000

By way of comparison, the Victorian State infection control (VICNISS) programme includes funding for the following positions1

• Director - 0.47 FTE

:

• Infection control nurses - 3.0 FTE

• ID physician - 0.4 FTE

• Epidemiologist - 1.0 FTE

• Operations Director - 1.0 FTE

• IT & Database support - 2.7 FTE

1 At the time of writing the VICNISS were not authorised to share the cost of the programme with us. The VICNISS programme has a wider scope - covering hospital acquired infections generally


• Biostatistician- 0.2 FTE

• Secretarial support - 1.0 FTE

Hosting the InterRai system – including software licences and support costs some $430,000 per annum. A further point of comparison is the contract with ESR for surveillance of notifiable diseases – which we understand is in the order of $6 million per annum – including laboratory costs.

The cost estimate is independent of who delivers the central agency functions. Options include the HQSC, a lead DHB, a university, HIQ, a Crown Research Institute, or a private provider.

3.2.3 One off central agency costs

In addition to the ongoing costs, the estimated one off implementation costs are set out below. The major establishment expense is setting up the national information system – estimated to be between $1 million and $1.5 million. A central agency system is required whether DHBs enter data manually or not – but the system is simpler to design and implement if it is simply a web based data entry portal (the Manual option).

Table 7: Central agency set up cost estimates

Central agency expense estimates $ one-off Automated Manual

Item Low Medium High Medium

DHB / sector engagement & project management 240,000 300,000 360,000 100,000

Information system specification and tender process(es) 20,000 25,000 30,000 15,000

Information system development, purchase and implementation costs 980,000 1,225,000 1,470,000 150,000

Post implementation review 16,000 20,000 24,000 20,000

Total 1,256,000 1,570,000 2,251,000 285,000

The division between central agency and local DHB costs is not fixed – one vendor estimated higher local and lower central agency costs than shown here. The important parameter is the total information system (IS) cost, which is shown at the end of this section.


3.3 Sizing the capacity needed to deliver the programme locally

3.3.1 Information sources

In order to estimate the ongoing costs of the program we wrote to all DHBs asking them to estimate the one off and ongoing costs of implementing the proposed programme. Nine were able to provide cost estimates – although many noted the large margin of error in their estimates. We have relied to a large extent on the international software vendor cost estimates.

3.3.2 Annual DHB SSI surveillance expenses

DHBs, on average estimated the ongoing cost of the proposed programme at $29,068 per annum per DHB – corresponding to $581,360 nationally. However the estimates ranged from $4,650 to $115,000, suggesting a high degree of uncertainty. We therefore modelled the costs on a bottom up basis.

The significant ongoing costs for DHBs are:

• Time spent collating and reporting data

• Information systems licensing and maintenance costs

Critical modelling assumptions are:

• DHBs already have an infection response capacity – as required under the health and disability sector standards – hence no additional cost is incurred in response activities (as opposed to surveillance activities)

• Manually collecting the SSI data specified in Appendix 1 would require the following amounts of time:

• If data collection is manual, 100% of the time required is additional to current infection control activities.

• If data collection is highly automated, the net cost of data collation in terms of staff time is nil – with any additional collation costs offset by savings in time spent on current infection surveillance activities.

Table 8: Time required to collect the dataset manually

Minutes per procedure/ SSI Cost per hour

Low Medium High

Denominator data (per surgery) 30 40 50 $36

Numerator data (per SSI) 15 20 25 $36


• Surveillance of procedures is based on the following procedure numbers and start dates:

Table 9: Programme procedure inclusions, estimated volumes, and start dates

Procedures Surveillance begins

Approximate annual volume of procedures

Hip and knee replacements Year 2 8,000 CABG Year 4 3,400

Caesars Year 4 15,000 Other1 Year 6 10,000 Other2 Year 8 10,000

With these assumptions, the cost of the programme to DHBs is dependent on the volume of procedures if a manual approach is taken, but not if the data collection is automated. Larger DHBs will do more procedures and therefore will face higher collation costs. The cost of CABG surveillance would fall entirely on the five DHBs that perform this procedure.

Table 10: Modelled ongoing cost ($) of SSI surveillance programme data collation and reporting, per year (medium) for all DHBs combined

Year / cost per year # procedures in

programme Collation costs Manual

option $ Collation costs Automated

option $

year 1 nil Set up only Set up only

year 2 7,966 195,008 286,000

year 3 7,966 195,008 286,000

year 4 26,655 652,514 286,000

year 5 26,655 652,514 286,000

year 6 36,655 897,314 286,000

year 7 36,655 897,314 286,000

year 8 46,655 1,142,114 286,000

year 9 46,655 1,142,114 286,000

year 10 46,655 1,142,114 286,000

Mean (9 years) 31,391 768,446 286,000

Table 10 shows the estimated collation costs under each option. Initially the manual option is cheaper, but as the number of procedures increases, the advantage of automated collation becomes apparent. Automated collation would have other spillover benefits, including making other hospital acquired infections easier to track. Further, if the volume of elective surgery continues to rise in line with demographic growth and ageing, then the cost of the manual processes would increase, whereas the automated system costs would not (although automated information systems will require periodic updating). An option would be to use manual processes for the


first tranche of procedures, and then invest in an automated system in year 4. The table above shows an average picture, but in practice smaller DHBs may find manual collation more cost effective than larger DHBs.

3.3.3 Estimate of One-off DHB implementation costs

DHBs estimated the one off costs of implementing the programme as per the summary below.

Table 11: DHB programme cost estimates ($)

Project management IS/IT Total

Mean 55,833 75,556 101,500

Range 0 - $106,000 $0 - $170,000 $20,000 - $276,000

DHBs were uncertain about the cost of developing information systems. Most have surgical audit databases that already collect most of the data, but a few do not. Some DHBs relied on quotes from infection control package vendors, others from r internal IS department estimates. An important cost driver and a key source of uncertainty is the cost of putting in place feeds from the three main information systems (laboratory, theatre and patient administration) in each DHB to the central repository.

Our bottom up costing comes to a higher value than the average DHB estimates – mainly because we have received specific vendor cost estimates for setting up the feeder systems and vendor fees, which most individual DHBs did not have access to. The table below summarises the one-off costs that were applied in the modelling.

Table 12: Estimated Local DHB automated SSI surveillance programme one off costs ($)

Cost component Cost per DHB - automated Manual

Low Medium High Medium

Local project management 28,000 35,000 42,000 20,000

Vendor fees - development, license, local implementation

79,160 98,950 118,740 -

Contingency 4,000 5,000 6,000 2,000

Total – per DHB 111,160 138,950 166,740 48,000

Total - NZ 2,223,200 2,779,000 3,928,500 960,000

The manual programme option avoids a number of one off up-front costs – at the expense of more nurse time spent data gathering in subsequent years. In practice,


costs by DHB will vary significantly depending on the ease with which feeds from existing systems can be customised.

One software vendor indicated that cost can either be front loaded – by purchasing licences up front, or back loaded through a lease arrangement. The expected life of the programme is unknown, but we have assumed that in year five, in the automated option, some repurchasing/upgrading is required at 50% of the cost of the original installation.

3.3.4 Time required to implement

Time to implement was also estimated by each responding DHB. The range was 6 months to 24 months, and the average 11 months. An approach to implementation is out of scope, but would likely include piloting of the system at one DHB and then progressive rollout region by region. One DHB expressed enthusiasm for being a pilot site. See the points raised is section 3.2.1 above re the necessity of signalling a national IS development well in advance.

3.4 Summary SSI programme costs

The table below shows the expected one off and annual costs for all DHBs combined and the central agency. Allowing for a 20% uncertainty range, an automated programme would cost the health sector between $3.5 million and $6.2 million to establish, and between $0.8 million and $1.2 million per year to run once established.

Table 13: Summary programme modelled costs, automated option, low medium and high cost scenarios

Cost scenario Cost component

Low Medium High year 1



(capital) year 2 -10

Local DHBs 2,223,200 228,800 2,779,000 286,000 3,928,500 343,200

Central agency 1,256,000 544,000 1,570,000 680,000 2,251,500 816,000

Total 3,479,200 772,800 4,349,000 966,000 6,180,000 1,159,200

The manual option costs significantly less to establish (medium estimate $1.2 million), but on average, more to run per year (medium estimate $1.25 million).

The automated option provides additional benefits associated with:


• Scale-ability – facilitates adding other hospital acquired infections over time (e.g. central line associated bacteraemia) and extending to other surgical procedures

• Accuracy – automated case detection would result in more consistent data collation and reporting and would avoid many transcription errors

• Timeliness – the automated approach is likely to give more timely data.

Given the slight advantage in cost, and the considerable advantage in functionality, we have assumed that the automated option is preferred.


4 Estimating benefits from SSI surveillance

4.1 Issues in calculating benefits

In order to calculate the financial benefit from surveillance we need to estimate:

• The current number of SSIs, and the current cost per SSI, giving a counterfactual (status quo scenario);

• The reduction in number of SSIs attributable to a national programme over time; and

• The cost savings from the reduction in SSI numbers.

To populate these parameters we requested data from DHBs from their current SSI surveillance activity, and supplemented this with a review of the international literature on SSI rates in comparable countries. We also requested data from ACC on treatment injury claims arising from SSIs. The DHB rates and literature review data are shown in detail in the appendix, and in summary below.

There are a number of sources of uncertainty in using the rates obtained from DHBs and the literature for modelling. The key issues are briefly described below.

4.1.1 Differences in case identification strategies

Some DHBs routinely use post discharge surveys (PDS) to help identify SSIs arising after discharge. Others count only SSIs that come to light during an admission or readmission. Some DHBs use discharge data to retrospectively calculate SSI rates, while other apply continuous surveillance methods using manual processes. The same differences complicate interpretation of international studies.

Use of post discharge surveys is known to markedly increase the number of SSIs identified. The proposed NZ surveillance programme does not include the use of post discharge surveys, hence, where the method is clear, we have excluded published international and DHB rates that include PDS as a mean of SSI identification. But some studies do not clearly state whether post discharge surveys are used, or they include some opportunistic post discharge surveillance (e.g. a tick box form at outpatient follow-up post surgery), but not post discharge surveys.

To accommodate this uncertainty we have modelled high, medium and low rates of SSIs.

4.1.2 Differences in infection type

Standard definitions divide infections into three categories:


• Superficial incisional infections

• Deep incisional infections

• Organ space infections

Superficial infections are much more frequent but have a significantly lower cost and morbidity than deep or organ space infections (for convenience deep and organ space infections are grouped together in this report – as they often are by DHBs). Post discharge surveys will tend to identify more superficial infections. We have included both superficial and deep/organ rates in our modelling, and assumed that the proportions of each type in NZ are roughly equivalent to those found in the reference studies – excluding those rates obtained using post discharge surveys.

Coronary artery bypass grafts have a further complication in that an infection can occur at the site where the vein was harvested (the leg), or at the chest incision site – and may also be superficial or deep/organ.

A final complication is that some international studies report rates by risk category, whereas most DHB SSI rates are not risk adjusted.

4.1.3 SSI rates

After review of the literature and DHB rates, and exclusion of rates obtained through post discharge survey methods, our estimate of the applicable rates for modelling in a NZ context are shown below. We have excluded most of the DHB data on CABG infection rates as two of the three DHBs reported rates involved post discharge survey based follow up2

. The DHB reported rates and the international rates are generally of the same order of magnitude as shown in the table below.

2 Of interest the excluded CABG infection rates were very high – a mean of around 22% SSIs – but these were predominantly leg (donor site) infections and were nearly all superficial.


Table 14: SSI rates per 100 operations (excluding post discharge survey numbers)

Category


Caesarean section Mean (SD) 2.7 (1.7) 2.4 (1.2) 2.5 (medium)

range 1.4 - 4.7 1.2 - 5.0 1.2 (low) - 3.8 (high)

Hip/knee JR Mean (SD) 1.9 (1.0) 1.6 (0.7) 1.7 (medium)

range 1.1 - 3.8 0.7 - 3.1 0.9 (low) – 2.6 (high)

CABG Mean (SD) 4.00 3.1 (1.4) 3.1 (medium)

range na 0.7 - 4.5 1.7 (low) - 4.6 (high)

Other SSI Mean (SD) 1.3 (0.7) 2.7 (0.9) 2.0 (medium)

range 0.3 - 1.7 1.6 - 3.8 1.0 (low) - 3.0 (high)

Implicitly we assume that the ratio of deep to superficial SSIs detected without PDS is approximately 1:1, except for Caesareans where the number of superficial infections will be higher3 4. The information on which these rates are based is shown in the appendix.

4.2 What reduction in SSI rates might be achieved through a national programme?

We reviewed the literature describing the experience internationally of the impact of surveillance programmes on SSI rates (see appendix for search strategy). Given that the impact of surveillance is central to this report, the studies are summarised in the table below.

Table 15: Impact of multi site surveillance & response programmes on surgical site infection rates

Study & brief description Impact on infection rates

Geubbels (2006) – Prospective multi-centre cohort study of acute care hospitals in The Netherlands. The surveillance comprised: Development of surveillance methodology by multidisciplinary team; use of a standardized registration protocol and software; regular training of data collectors; anonymous inter-hospital comparison of infection rates and feedback of results; appointment of one contact person per hospital, responsible for data collection; and dissemination of results to other health care professionals. Regular discussion of both successful and failing prevention strategies that had been instituted based on the surveillance

The risk of infection was reduced for patients who had an operation during the fourth surveillance year (RR = 0.69; 95% confidence interval (CI) = 0.52–0.89) and decreased further for patients operated on during the fifth surveillance year (RR = 0.43; CI = 0.24–0.76) as compared with patients who underwent surgery within one year of the start of surveillance in their hospital. No significant risk reduction was observed for patients operated on during the second and third surveillance years. The incidence of SSI remained relatively stable at around 4.3% in the first three surveillance years and then dropped to 3.3% in the fourth year and



results5. Period: 1996 - 2000

further down to 1.8% in the last surveillance year. Concludes that surveillance, supported by participation in a surveillance network reduced the risk of SSI in surgical patients registered in the Dutch surveillance network PREZIES.

Brandt et al 2006, looked at 130 surgical departments of German hospitals participating in the Krankenhaus Infektions Surveillance System (KISS)6. Retrospective multiple logistic regression analyses. Departments’ SSI rates were calculated individually for each year of surveillance and for each operative procedure category, taking into account when the individual departments had begun their surveillance activities. Active SSI surveillance was performed according to National Nosocomial Infections Surveillance system (NNIS) methods and definitions. Period: 1997 - 2004

For 14 of 19 operative procedure categories analyzed, there was a tendency toward lower SSI rates that was associated with increasing duration of SSI surveillance. In multiple logistic regression analyses of pooled data for all operative procedures, the departments’ participation in the surveillance system was a significant independent protective factor. Compared with the surveillance year 1, the SSI risk decreased in year 2 (odds ratio, 0.84; 95% confidence interval, 0.77-0.93) and in year 3 (odds ratio, 0.75; 95% confidence interval, 0.68- 0.82), and there was no change in year 4. The study concluded that the SSI incidence was reduced by 25% as a result of the surveillance-induced infection control efforts over 4 years.

Gastmeier et al 2006 “The aim of this study was to investigate whether participation in the German national NI surveillance system [KISS] resulted in reduced rates of NIs….. Only institutions that had participated in KISS for at least 36 months were considered for analysis7. Data from the first 12 months of surveillance were compared with data from the second and third 12-month periods. Period: 1997 - 2003

The average SSI rate in the surgical inpatients was 1.6 per 100 operations in their first year of participation. Comparing the infection rates in the third year with the first year…..The corresponding RR for SSI was 0.72 [95% CI0.64-0.80]. Participation in KISS was associated with a significant reduction in the three types of infection rates included in the study

Barwolff et al (2006) used KISS data to assess whether surveillance and feedback of healthcare associated infections could reduce the infection rate after caesarean delivery (CD)8 9. Only departments that had participated in KISS for at least three years were included in the analysis. 26 obstetric and gynaecology departments met the study’s inclusion criteria. Post discharge surveillance is not performed routinely as part of the KISS, but SSIs that become evident after discharge are also included. Period: 1997 - 2003

“In those 26 departments, 17405 CD procedures were performed and 331 SSIs were recorded (1.9%). The SSI rate after CD procedures was significantly reduced in the third year of KISS participation (1.6%), compared with the first year of KISS participation (2.4%), with a relative risk of 0.63%. Logistic regression analysis confirmed that KISS participation over three years was an independent factor in the reduction of SSI rate (odds ratio 0.64; 95% CI 0.49 – 0.83).



Rioux et al (2007) looked at the results from a six year surveillance system amongst volunteer surgical wards in hospitals from Northern France9. Surgical wards did not necessarily participate in the study every year. Patients were followed for 30 days following surgery. A dash board was displayed at the end of each annual survey, so that participants could compare with other surgery adjusted for National Nosocomial Infections Surveillance Included post-discharge monitoring until 30 days (via appointment with the surgeon post discharge). 1988 -2003

Over six years the crude SSI incidence decreased from 3.8% to 1.7% and the NNIS-O3

SSIs were superficial in 64.3% of cases, and deep or organ/space in 35.7%. 21.6% of cases required re-operation.

adjusted SSI rate fell from 2% to 1%. The authors conclude that an active surveillance system striving for benchmark through a network is an effective strategy to reduce SSI incidence.

54.4% of SSIs were diagnosed in patients during the hospital stay.

Astagneau et al (2009) estimate the reduction in surgical site infection incidence through the French ISO-RAISIN surveillance system10. Evaluated the impact of an eight year national SSI surveillance system. Consecutive patients were enrolled [in the study] during a three month period each year and surveyed for 30 days following surgery. 1999-2006

“Both crude and NNIS-0 SSI incidence decreased significantly by 38% and 32%, respectively, between 1999 and 2006. The decrease in SSI incidence was not linear, and was mainly apparent in the first three years, followed thereafter by fluctuating decrease from 2002 to 2006. A similar temporal trend was observed for relative risk estimated in the multivariate analysis showing a reduction by 30% between 1999 and 2006. The proportion of superficial v deep incisional or organ space SSI decreased over the study period (61.0% in 1999 v 54.5% in 2006)” Found a significant reduction over the period in reported rates of SSI for Caesarean section (-56%) and or hip prosthesis (-36%) patients

Carlet et al (2009) report on the French ISO-RASIN programme, looking at surgical site infection rates between 1999 and 200511.

They found that SSI rates for major surgical procedures declined by 31% for overall incidence and 29% for NNIS risk class 0.

Mannien (2008) chapter 6 evaluates the time trend in surgical site infection rates in relation to the duration of surveillance in the Netherlands12. Uses data from 42 hospitals that participated in PREZIES between 1996 and 2006 and registered information for at least three years on one of the five procedures. Surveillance time to operation was stratified in consecutive 1 year periods, with

For total hip prosthesis the SSI rate decreased significantly by 6% per surveillance year, indicating a 60% decrease after 10 years. Over a ten year period, an average decreasing trend in SSI rates for knee prothesis of 3% per surveillance year, although this result was not statistically significant at the 95% CI. “Even though most decreasing trends in SSI rate

3 National Nosocomial Infections Surveillance system (NNIS) is a risk index of likelihood of patient developing an SSI.



the first year as reference. All models were adjusted for method of post discharge surveillance. 1996-2006

were not statistically significant, they are encouraging. To use limited resources as efficiently as possible, we would suggest switching the surveillance to another surgical specialty when the SSI rate has decreased below the target.”

Segers et al 2006 report on the impact of a risk control programme including surveillance on the incidence of surgical site infections13. The study was specific to cardiothoracic surgery at the Academic Medical Centre, Amsterdam. 3009 cardiothoracic surgical procedures were reviewed. Period: 2001 - 2003,

After starting the surveillance programme a steady decline in prevalence was observed from 8.9% to 3.9%. “This adds to the evidence that SSI after cardiothoracic surgery is a major but mainly preventable cause of morbidity and mortality.” For deep SSIs, overall mortality declined from 6.6% to 3%.

To ensure studies are as relevant as possible, we have excluded surveillance impact reports that were limited to one or two hospital locations; restricting the studies to multi-site comparisons that were published in the peer reviewed literature in the period 2006 – 2011. Nonetheless, we acknowledge that these studies may suffer from time bias (as techniques for preventing SSIs spread rates may come down generally) and from sample biases (working with enthusiasts). However, at least some studies have controlled for the time bias by comparing performance over time amongst those in and out off the surveillance programme.

Overall, we estimate that the international experience is for a reduction of some 8% per year (+/- 4%) (See below).


Table 15: Summary reductions in SSI rates from international studies

Study ref Impact on infection rates Straight line rate / year %

Geubbels (2006) 58% reduction over 5 years 11.6

Brandt (2006) et al 2006, 25% reduction over 4 years 6.25

Gastmeier et al (2006) 28% reduction over 3 years 9.3

Barwolff et al (2006) 36% reduction over 3 years 12

Rioux et al (2007) 55% reduction over six years. 9.1

Astagneau et al (2009)

56% reduction in caesarean SSI over 7 years 36% reduction in Hip SSI 7 years

8 5.1

Carlet et al (2009) 31% reduction over 6 years 5.16

Mannien (2008) 60% decrease for hips over 10 years 30% decrease for knees over 10 years

6 3

Segers et al (2006) 56% reduction over 3 years 18.6

All studies Mean 8.6

All studies Std dev 4

We have used the following as modelling parameters for the reduction in SSI rates post implementation. A large margin of error is included to reflect the diversity in study findings, and the difficulty in accounting for bias.

Annual rate of reduction in surgical infections year one reduction

• Low: 4%

• Medium: 8%

• High: 12%

Table 16: Maximum cumulative reduction over the ten year period (adjusting for start dates as applicable).

low Medium high

Knees 30% 50% 70%

Hips 30% 50% 70%

CABG 30% 50% 70%

Caesareans 30% 50% 70%

Other 1 20% 35% 50%

other 2 10% 20% 30%


The maximum is capped at a lower rate for the ‘other’ procedures because they are introduced at a later time into the programme. We have assumed the following schedule of surveillance over the next ten years.

Table 17: Number of surgical cases included in the surveillance programme

Year

1 Year 2 Year 3 Year 4 Year 5 Year 6 Year 7 Year 8 Year 9 Year 10

Hips 4347 4347 4347 4347 4347 4347 4347 4347 4347

Knees 3619 3619 3619 3619 3619 3619 3619 3619 3619

CABG 3444 3444 3444 3444 3444 3444 3444

Caesars 15245 15245 15245 15245 15245 15245 15245

Other 1 10000 10000 10000 10000 10000

Other 2 10000 10000 10000

Total 7966 7966 26655 26655 36655 36655 46655 46655 46655

The assumptions on incidence, and on reductions achieved, result in the following modelled trends in numbers of infections per annum.

Figure 3: Estimated annual number of surgical site infections in selected elective procedures in the surveillance programme, medium scenario

Yr1 Yr2 Yr3 Yr4 Yr5 Yr6 Yr7 Yr8 Yr9 Yr10

Knee replacements 62 56 52 48 44 41 38 35 32 30

Hip replacements 74 68 63 59 55 51 47 44 40 37

CABGs 107 107 107 98 90 83 75 68 60 53

Caesarian sections 377 377 377 347 318 291 265 239 213 188

Other1 200 200 200 200 200 184 170 156 143 130

Other2 200 200 200 200 200 200 200 184 171 160

-

50

100

150

200

250

300

350

400

SSIs

Year

Knee replacements Hip replacements CABGs

Caesarian sections Other1 Other2


4.3 Estimating the cost savings associated with a reduction in SSIs

We reviewed international and available DHB data on the additional cost of treating patients with an SSI. The available cost data suffers from a number of limitations including:

• International studies reflect the cost of service provision in their jurisdiction, and may not be directly convertible to NZ costs

• Studies with different case detection methods will have different rates of superficial SSIs and may be comparable to NZ rates

• DHBs can often only provide the cost of an inpatient stay – whereas an SSI may involve treatment with IV antibiotics for a number of weeks in a home environment;

• Costs generally only include the cost to the health provider or funder – the cost to society (e.g. through time off work) is not often captured.

• Recent papers have suggested that most SSI impact studies suffer from a time bias effect – implying that the higher average length of stay in SSI cases is over-estimated14.

In addition to the above issues, the extent to which savings from reduced SSIs can actually realised at the DHB level will vary. Smaller DHBs may be running nursing and medical staffing levels that are driven by the need to provide 24/7 care, rather than by volumes. Some DHBs may be able to increase surgical volumes and earn additional revenue if their infection rates drop, others may not. The actual financial impact of an SSI case may vary significantly from the usual resources time average cost equation used to calculate impact. For instance, an infected CABG that ties up an ICU bed for a number of days may result in cancellations of a number of planned surgical cases and significant lost revenue opportunities. Alternately, a reduction of ten bed days in a provincial centre may result in little real savings.

We looked at three data sources to estimate likely cost per SSI and hence savings per SSI avoided:

• Impact on average length of stay plus community care component

• Impact on health sector resources (cost)

• Cost to ACC

These are described briefly below.

4.3.1 Impact on average length of stay

Table 10 shows estimated impact on ALOS based on international studies reviewed.


Table 18: Impact of SSIs on average length of stay (excess days)

Low (less 20%)

Medium (mean rates)

High (plus 20%)

Knee JR 11.8 14.8 17.8

Hip JR 11.8 14.8 17.8

Caesars 4.6 5.8 6.9

CABGs 16 19.8 24

Other 8.0 10.0 12.0

These estimates need to be treated with some caution, given that time bias effects are not controlled for in most studies.

4.3.2 Estimating cost based on impact on health sector resources

Studies have generally found that the cost of treatment increases by more than the increase in length of stay2. Hence we also used published estimates of costs for the relevant procedures and converted them into NZ$ at the relevant year using World Bank purchasing power parity exchange rates. After inflating the estimates for cost growth to the year 2010 we obtained the following costs per SSI.

Table 19: Cost of SSI estimates from literature review, $NZ PPP adjusted to 2010

Summary cost of SSI $NZ PPP adjusted

Misc Hips/knees Caesars CABG

Scott – low estimate 12,348

Scott – high estimate 33,008

Olsen

3,819

VICNISS 2006

42,207 Edwards

42,686

Coello superficial

6,590

8,134

Coello deep

16,535

16,646

Alfonso 11,747 Counties Manukau DHB 9,097

ADHB

51,773

Median 12,047 29,371 3,819 16,646 Mean 16,550 27,004 3,819 25,518 Typical NZ CWD cost 2010/1115 n.a. 16,000 5,200 26,000

For comparison we have shown the usual CWD cost in 2010/11 caseweights for the


equivalent procedures (with no infection). A general rule of thumb is that an SSI more than doubles the cost of the original procedure.

The studies from which this median is obtained are shown in the appendix, other than the Counties Manakau data, which was sent to us directly. We did not include studies from the United Sates as their cost structure is quite different to those seen in the NZ health sector. The studies will include a combination of deep and superficial SSIs and will have been generated using different methods. Some will include community care costs and some will not. A recent review of the accuracy of economic studies on SSIs concluded that because of the heterogeneity of methods, “At present it seems to be extremely difficult to compare the results of cost analyses in different temporal and spatial contexts.”16 Hence these cost estimates should be viewed sceptically.

4.3.3 ACC costs

ACC treatment injury unit provided the following information on claim numbers and costs for healthcare infections post surgery in the procedures of interest.

Table 20: Cash Costs for Accepted Healthcare-Associated Infection Claims for Selected Surgical Types: 1 Jul 2005 – 26 Mar 2011

Event Number of

Accepted Claims up to 26 Mar 2011

Net Cost at 26 March 2011 (to nearest $100)

Median Net Cost

Average Net Cost

Sum of Net Cost

Caesarean section 122 $200 $4,400 $536,000 Coronary Artery Bypass Graft (CABG) 83 $400 $2,700 $222,000

Hip surgery / replacement 230 $1,000 $14,800 $3,403,000

Knee surgery / replacement 296 $400 $9,800 $2,895,000

The claim costs are not easily converted to annual impact on health sector. They cover costs over a number of years in some cases, include large numbers of claims that have no payment (e.g. for injury arising from treatment in a public hospital where payment is made through the public health acute levy), and they include income related compensation. For accepted claims with infection-related injury types arising from Caesarean section, CABG, Hip and Knee surgery and replacements, the percentage of cash costs spent on the following types of assistance were:

• Treatment costs: 40.5%

• Independence allowance and lump sums: 4.1%

• Weekly compensation: 28.9%

• Vocational rehabilitation 1.3%


• Support for Independence (social rehab): 23.2%

ACC is likely to have a major interest in reducing rates of surgical site infections, but their claim costs are not useful in establishing cost saving parameters for this CBA.

4.3.4 Summary cost reduction estimate

The medium cost savings estimate used in this CBA is shown in the table below. The cost per SSI is an important determinant of the profit or loss associated with the programme overall, and the real rate is uncertain, hence we have run scenarios varying the cost by plus or minus 20%. We have taken a conservative view of the savings per SSI, in part to recognise the partially fixed nature of healthcare costs, the unknown effects of differences in casemix, and the likely bias in published studies.

Table 21: Summary savings per SSI avoided estimates, medium scenario

Savings per SSI avoided

Knee JR Hip JR CABGs Caesars Other

Based on ALOS $15,253 $15,253 $17,733 $6,149 $9,955

Based on health cost studies (mean)

$27,004 $ 27,004 $ 25,518 $3,819 $16,550

Modelled (+/- 20%) $ 21,000 $ 21,000 $20,000 $4,500 $10,000

4.4 Estimated benefits from SSI surveillance

Table 15 shows the impact of the estimated baseline numbers of SSIs, the number avoided through the impact of the programme, and the savings from avoided SSI’s by year. Savings are shown in constant 2011 $, with no discount rate applied.

Table 22: Forecast SSIs, and costs avoided over ten years, for procedures included in the surveillance programme

Procedure Knee JR Hip JR CABGs Ceasar Other1 Other2 Total SSI's

SSI's avoided

Savings

Cost / SSI 21,000$ 21,000$ 20,000$ 4,500$ 10,000$ 10,000$ Yr1 62 74 107 377 200 200 1,019 - Yr2 56 68 107 377 200 200 1,007 12 248,301 Yr3 52 63 107 377 200 200 998 21 437,180 Yr4 48 59 98 347 200 200 951 68 913,066 Yr5 44 55 90 318 200 200 908 111 1,356,972 Yr6 41 51 83 291 184 200 850 169 1,940,992 Yr7 38 47 75 265 170 200 795 224 2,495,511 Yr8 35 44 68 239 156 184 725 294 3,190,591 Yr9 32 40 60 213 143 171 661 359 3,839,246 Yr10 30 37 53 188 130 160 598 421 4,460,463

Total 1,678 18,882,320


The benefits from the programme build steadily as the modelled infection rates decrease, and the number of procedure types in the programme increases. Savings against the counterfactual are cumulative, based on the assumption that SSI incidence rates would, in the absence of the programme, remain at current levels. By year ten savings from SSIs avoided are estimated at $4.4 million per annum. These savings continue indefinitely. Savings to ACC through reduced employment compensation payments have not beenincluded.

4.4.1 Non-financial benefits

Possible benefits not modelled include:

• potential reductions in infection rates in surgical procedures not included in the programme through adoption of best practice operating theatre practices

• better management and control of MRSA

• reduced deaths – estimates are that the mortality rate associated with surgical site infection is between 2% and 4.5% 2 17

• quality of life gains – some of those who contract a deep or organ space surgical site infection have enduring disability and pain associated with the infection

Estimated cost of elective procedure SSIs in NZ

The data collected in this report can be used to make a rough estimate the cost of elective SSIs in NZ. There are some 132,000 publicly funded elective discharges per year in NZ. If the incidence of surgical site infections lies between 1% and 3%, and the average cost per SSI is between $10,000 and $15,000, then the cost of publicly funded elective surgical SSIs is between $13.2 million and $59.4 million.

Table 23: Indicative cost of elective SSIs in NZ

Cost per SSI

SSI rate $ 10,000 $ 12,500 $ 15,000

1% $ 13,200,000 $ 16,500,000 $ 19,800,000

2% $ 26,400,000 $ 33,000,000 $ 39,600,000

3% $ 39,600,000 $ 49,500,000 $ 59,400,000

This calculation is presented for information only, and is not used in this report. However the figures illustrate the fact that the cost of SSIs – and the potential savings - are driven to a large extent by the incidence of SSIs. A similar estimate in the US calculated the cost of SSIs there as being between $US3 billion and $US10 billion per annum1.


5 Is a national surveillance programme a worthwhile investment?

This section takes the estimated costs of running the surveillance programme and the estimated benefits and combines them to calculate the net benefit.

5.1 Ten year costs and benefits

The table below shows key model outputs based on applying the assumptions set out in sections three and four of this paper.

Table 24: Ten year estimated summary costs and benefits,automated scenario

Cost / benefit Medium scenario Credible range

Surveillance programme costs

One off costs $4.4 million $3.4 - $5.1 million

Annual cost $1 million $0.8 - $1.2 million

Cumulative ten year costs $15.8 million $12.5 - $20.3 million

Surveillance programme benefits

SSIs avoided (ten years) 1,678 473 – 3,641

SSI costs avoided - ten year savings $18.8 milion $4.4 - $49 million

SSI costs avoided – annual savings at year 10 $6.2 million $1.1 - $11 million

Bed days freed up 19,765 5,793 – 42,000

Deaths avoided (ten year total) 50 14 – 109

The large credible range is a result of the number of parameters that have been estimated and the level of uncertainty surrounding their values. In practice, values are more likely to lie closer to the medium scenario than to the best or worst case scenarios – it is unlikely that circumstances will align such that the programme costs will be higher than anticipated, and the SSI rates will be lower than expected, and the SSI cost will be lower than epxected, and the effectiveness of programme will be lower than modelled.


5.2 Estimating Net Present Value

The cashflow forecast for the medium case (automated scenario) is shown below.

Table 25: Costs and benefits of the proposed SSI surveillance programme, by year, automated option, medium case

Using a discount rate of 3.5%,4

Table 26: Ten year net present value of best, middle and worst case combination of SSI surveillance programme parameters in automated and manual scenarios at 3.5% discount rates

this gives a net present value of $0.94 million in the medium scenario – meaning that the health sector would be better off financially over the ten year period by investing in the surveillance programme. However, the picture varies considerably, from a worst case of negative $14 million, to a best case of positive $27 million – as summarised in table 26.

Case Automated data collation NPV

Best case $ 26,901,808

Medium Case $ 941,296

Worst case - $ 14,200,428

4 Pharmac,‘Prescription for Pharmacoeconomic Analysis - Methods for Cost-Utility Analysis’ (May 2007), Available at www.pharmac.govt.nz/2007/06/19/PFPAFinal.pdf

Savings from avoided SSIs ($)

Programme capital cost ($)

Programme ongoing cost ($)

Net cashflow ($)

Discounted cashflow @ 3.5%

Yr1 -4,369,000 -483,000 -4,852,000 -4,687,923Yr2 248,301 0 -966,000 -717,699 -669,980Yr3 437,180 0 -966,000 -528,820 -476,966Yr4 913,066 0 -966,000 -52,934 -46,129Yr5 1,356,972 0 -966,000 390,972 329,188Yr6 1,940,992 -2,184,500 -966,000 -1,209,508 -983,936Yr7 2,495,511 0 -966,000 1,529,511 1,202,182Yr8 3,190,591 0 -966,000 2,224,591 1,689,380Yr9 3,839,246 0 -966,000 2,873,246 2,108,190Yr10 4,460,463 0 -966,000 3,494,463 2,477,290Total 18,882,320 -15,730,500 3,151,820 941,296

http://www.pharmac.govt.nz/2007/06/19/PFPAFinal.pdf�


The most important driver of whether the programme would be cost effective or not, is the actual incidence of SSIs: if the lower estimates of incidence values in Table 14 are applied, then the NPV tends to be negative, if the high incidence values in Table 14 are applied the NPV is positive. Unfortunately it is impossible to remove the uncertainty as to what the actual SSI rates in New Zealand are, in the absence of a nationally consistent surveillance programme.

The best and worst cases are unlikely to eventuate. The more likely scenarios are shown below.

Table 27: NPVs by scenario, showing key assumptions, using 3.5% discount rate

Key assumptions

Scenario (all automated)

Programme cost level

SSI Incidence

Average cost per SSI

Reduction in SSI incidence

10 year NPV ($)

Medium case Medium Medium Medium Medium 941,296

Low incidence / high cost

Medium Low High Medium -4,545,690

Low incidence / medium cost

Medium Low Medium Medium -6,049,829

High incidence / low cost

Medium High Low Medium 3,995,553

Medium incidence / low cost

Medium Medium Low Medium 225,933

Terminal value These NPVs do not provide for a terminal value – i.e. for the ongoing savings into the future from an SSI surveillance programme. Including a terminal value would make the NPV positive in any reasonable scenario. However, beyond ten years the uncertainties multiply, making it unlikely that ongoing savings after year ten could be considered bankable.

5.3 Issues requiring resolution as part of the next stage of the project

Key informants consulted in the course of this CBA raised the following issues which are outside the scope of this paper to address, but which may need to be considered in a national rollout:

• The difficulty in identifying readmitted cases – without an automatic alert.

• The difficulty identifying cases where someone is readmitted at a hospital other than where they were operated on.


• The option of using ICD 10 codes as a proxy for admissions (noting that some participants favour this and others consider it to be substandard in that it does not allow risk adjustment of SSI rates).

• The use of post discharge surveys – again respondents are split on the use of these.

• The opportunity to include private surgical activity – for instance by making disclosure of SSI rates a requirement for licensing.

• Public reporting rules (accommodating small numbers, surgeon details, etc).

• Interface with the NZ Joint Register – to avoid duplicate data collation & entry.

At the time of writing the State of Victoria had nearly completed a review of their state-wide infection surveillance programme. Their findings may be pertinent to decisions on a NZ programme.

5.4 Limitations

This report has a number of important limitations:

• The data used to derive the model assumptions are subject to considerable uncertainty – this has been addressed to the extent possible through the use of plausible scenarios.

• The calculated benefits exclude societal benefits, or spillover benefits to other surgical procedures or to privately funded operations, and to this extent may be understated.

• The counterfactual is assumed to be the status quo – whereas in practice infection rates may change over time regardless of whether the programme is introduced.

• The information systems costs estimates have not been validated through a contestable process.

• The cost savings per SSI have not been apportioned between the fixed and marginal costs of treatment – but a relatively conservative approach to costing SSIs has been adopted to ameliorate the risk of overstating savings.

• Data from international studies has been used to supplement information from NZ: applying international rates is known to be imprecise given differences in case identification approaches, costing methodologies and health sector context.

5.5 Conclusions

We draw the following conclusions from this cost benefit analysis:


5. A national SSI Surveillance Programme is highly likely to lead to significant reductions in surgical site infection rates

The evidence for this conclusion is the experience internationally across a number of countries, the Southern Cross experience, and the reported changes in rate at DHBs when they have introduced surveillance of particular procedures. We calculate that a surveillance programme could plausibly avoid some 1,678 surgical site infections in its first ten years.

6. The financial case for a surgical site surveillance programme is positive, but not under all scenarios

An automated SSI surveillance programme is likely to cost some $4.4 million to introduce, plus ongoing costs of some $1 million per annum to maintain. The medium (most likely) case gives a positive net present value of $0.9 million over ten years, using a discount rate of 3.5%. However, if the real incidence of serious SSIs is significantly lower than expected, then the NPV becomes negative - with a value of negative $6 million not unlikely.

7. Automated surveillance is likely to be superior to manual surveillance The automated option costs a similar amount to the manual option, and generates substantial spillover benefits in terms of ongoing costs savings and the ability to extend the programme to cover other procedures/infection types. However, this finding is very sensitive to estimates of the cost of the information systems. We suggest further work with DHBs and the NHIT board if a programme is to be introduced, as an automated system is likely to be beneficial in the long run, but manual data collation is better in the short to medium term.

8. An economic CBA is likely to be strongly positive Notwithstanding the conclusion that the NPV is only marginally positive, an economic CBA – including the cost of time off work and other societal costs - would be very likely to result in a strongly positive NPV in all reasonable scenarios.


6 Appendix

6.1 Indicative Surgical Site infection dataset to be provided by DHBs

The proposed data set to be centrally reported as recommended by the NQIP working group in March 2010, is set out below. The fields will require further definition if we decide to proceed. Many of the data items are already collected and reported as part of the national minimum dataset. Others are not currently reported, but in many DHBs will be collected as part of the theatre, pharmacy, laboratory or clinical audit systems. The issue will generally be linking these databases so that a consolidated report can be prepared with a minimum of manual data entry.

Source: Recommendations for a national procedural and infection surveillance programme, March 2010.


6.2 DHB reported SSI rates

The following rates were supplied by DHBs in support of this CBA.

Notes:

• PDS means post discharge survey.

• Rates were gathered over different time periods and using differing methods – hence they are not directly comparable.

6.3 Southern Cross Hospitals Limited Surgical Site Infection Surveillance Programme

Southern Cross Hospitals introduced a nationally consistent surgical site infection surveillance programme in 2004. It now covers 13 Southern Cross Hospitals Ltd owned or affiliated hospitals. This is the only significant multi site SSI monitoring programme in NZ. The information system that supports the programme was developed as a besoke application and is hosted centrally with local access via the internet for data entry

DHB N % SSI N2 % SSI2 % deep N % SSI4 N 22 % SSI3 Includes PDS?DHB 1 200 7.5% 400 (approx) 2.3% yesDHB 2 128 9.4% 124 4.8% 86 8.1% yes

DHB 3 350 4.7% 210 1.1% no

DHB 4 146 1.3% 100.0% yesDHB 5 1549 1.9% 369 0.3% noDHB 6 97 3% 119 5.0% yesDHB 6 825 1.7% noDHB 7 74 1.4% 67 1.5% no

DHB 8 147 14% 136 27.9% 92 14.0% yesDHB 9 450 3.8% no

DHB 10 74 6.5% 161 6.3% 20 16.5% yesDHB 11 inhospital only 186 2.2% 100 2.0% 100 4.0% noDHB 11 total 186 9.1% 100 5.0% 100 23.0% yesDHB 12 1556 5.3% 20.8% 35253 1.2% y/n

Mean 6.5% 3.0% 17.9% 5.1%std 4.1% 1.8% 10.4% 5.3%Weighted mean 1442 6.5% 4463 3.5% 356 19.2% 36744 1.3%Mean excl PDS 2.8% 2.5% 4.0% 1.1%

SSI otherLSCS Orthaepedic / TJR CABG


and report generation. The Southern Cross Hospitals system includes all the data fields proposed for the national SSI surveillance programme, but also includes a 30 day post discharge survey sent to patients. Over all their hospitals the current averaged response rate is 83%.

Data collection is mainly manual, with theatre staff entering the relevant data onto a paper form, and ward staff including any further required information. The form is then sent to the infection control nurse who organises data entry. Positive responses from the post discharge survey are followed up by the infection control nurse by calling the surgeon or GP to validate the infection. Southern Cross Hospitals provide a list of recommended procedures for monitoring, but, in addition, each hospital has some discretion about which other procedures it targets. The recommended procedures for monitoring are:

• Orthopedics: joint replacement procedures (hip, knee, ankle and shoulder replacements).

• General Surgery: herniography, thyroidectomy, mastectomy (wide excision).

• Gynaecology: hysterectomies (vaginal, laparoscopic, laparoscopic assisted, abdominal).

• Vascular: abdominal aortic aneurysm repairs, endartarectomies, varicose veins.

• Plastic and Reconstructive: breast surgery, abdominoplasties.

• Cardiac: CABG, Valve Replacement.

Small hospitals might follow up all or nearly all procedures of certain types (to get sufficient data), whereas larger hospitals may do only a 2 or 3 month sample.

Southern Cross report that they have seen a reduction of 25% in the SSI rate since the programme was introduced. The data also allow them to identify when some hospitals have increased rates for periods of time and to provide information on potential actions to support SSI response. Southern Cross Hospitals consider the actual rates to be confidential and do not release them publicly, but each hospital sees its rates compared to others.

6.4 Literature review

6.4.1 Studies estimating rates of infection by procedure – general findings

Coello (2005) comments that “…it is likely that the postoperative LOS differs between countries; if patients, in general, remain longer in hospital in England, it is likely that more infections will be detected.” in explaining differences between higher rates of infection in England than in the US. 2


Wilson (2007) compares definitions for infection between the UK and US and finds marked differences in patients defined as infected following cardiac surgery. A high proportion of infected wounds are only identified during post-discharge follow-up.18

Mannien 2008 contains a chapter that shows statistical evidence from the PREZIES network on the importance of post-discharge monitoring. Up to 79% of SSI associated with knee prosthesis surgery may occur after discharge. “Over the past decade, there has been an increasing trend toward shorter length of hospital stay and use of ambulatory day surgery. Thus, an increasing proportion of SSIs occur after the patient has left the hospital, which makes post discharge surveillance (PDS) increasingly important.”12

Reilly et al (2008) undertook a national point prevalence survey of HAI in Scotland and found 197 cases of SSI amongst 11608 patients in acute care hospitals (1.7%). 19

Avato & Lai (2002) estimate that only 28% of the surgical site infections for coronary artery bypass procedures would have been detected if surveillance had been limited to hospital stay. 40% of SSI were detected on readmission, 28% on outpatient follow ups. Study was undertaken at a US at a hospital that is a tertiary care referral center for surrounding hospitals.20

Barnes et al (2006) also undertook a study of the difference between prosthetic joint replacement infection rates in a large integrated healthcare system using a standard surveillance system inclusive of the post discharge period with the NNIS rates. NNIS does not require post discharge surveillance. Rates with post discharge surveillance were much higher21.

NICE (October 2008 Costing Statement) “At least 5% of patients undergoing a surgical procedure develop a surgical site infection.”22

Mannien (2008) in the Netherlands approximately 3% of surgical patients develop a surgical site infection. 12

Chapter 5 in Mannien (2008), in comparing the PREZIES and KISS infection surveillance data, that “In conclusion, even though similar infection surveillance protocols were used in the Netherlands and Germany, differences occurred in the implementation. Comparison between countries are most reliable if only deep SSI during hospitalization are taken into account, since these SSI are not affected by postdischarge surveillance and the diagnostic sensitivity for deep SSI is probably more alike between countries than for superficial SSI.”12

Healthcare Associated Infection Surveillance Western Australia (HISWA)

The Healthcare Associated Infection Surveillance Western Australia (HISWA) was established as a voluntary program for both private and public healthcare facilities in


2005. Mandatory reporting of specific healthcare associated infections was introduced for all public hospitals and those private hospitals contracted to provide services for public patients in 2007.

Current HISWA Indicators

1. Surgical site infections following hip or knee arthroplasty. 2. Central-line associated bloodstream infections 3. Haemodialysis access-associated bloodstream infections 4. Methicillin resistant Staphylococcus aureus (MRSA) infections 5. Staphylococcus aureus (MSSA & MRSA) bloodstream infections 6. Occupational exposures to blood or body fluids 7. Clostridium difficile infection (commencing January 2010)

HISWA recent data (refer http://www.public.health.wa.gov.au/3/449/3/about_hiswa.pm) are shown below.

Huotori et al (2010) evaluated the Finnish hospital infection program (SIRO) conducting incidence surveillance for prosthetic joint infection (PJI) from 1999 to 2004, looking at hip and knee anthroplasties. Using capture-recapture estimating, the PJI rate was estimated at 2.1% for hips and 1.5% for knees – which was higher than predicted by the national sentinel surveillance systems. 23

Szilagyi et al (2008) examined data from the Hungary surveillance system for nosocomial infections between Nov 2004 and October 2006, representing 25% of Hungary hospitals. The definitions of surgical procedures and SSI, the surveillance methodology and patient risk index categories were those established by NNIS. The SSI rate amongst surgical patients was overall 2.27%, caesarean 1.31% and hip replacement 2.91% (crude figures). Data according to risk categories is also presented. 24

http://www.public.health.wa.gov.au/3/449/3/about_hiswa.pm�


6.4.2 Caesarean section SSI rate findings

Olsen 2010 estimates 5% of low transverse caesarean patients develop SSI in Barnes-Jewish Hospital, a tertiary care hospital affiliated with Washington University School of Medicine in Saint Louis, Missouri. 25

Rioux et al (2007) found SSI in 3.08% of caesarean sections. The study included patient follow up for 30 days following surgery. 9

Russo et al (2006), VICNISS (Victoria, Australia) data between November 2002 to December 2004 give an implied crude SSI rate of 2.1% of caesarean patients (calculated from data in table 2 of paper).26

Barwolff et al (2006) used KISS data to assess whether surveillance and feedback of healthcare associated infections could reduce the infection rate after caesarean delivery (CD). Only departments that had participated in KISS for at least three years were included in the analysis. Post discharge surveillance is not performed routinely as part of the KISS, but SSIs that become evident after discharge are also included. 26 obstetric and gynaecology departments met the study’s inclusion criteria. “In those 26 departments, 17405 CD procedures were performed and 331 SSIs were recorded (1.9%). The SSI rate after CD procedures was significantly reduced in the third year of KISS participation (2.4%), with a relative risk of 0.63%.....Logistic regression analysis confirmed that KISS participation over three years was an independent factor in the reduction of SSI rate (odds ratio 0.64; 95% CI 0.49 – 0.83).8

Szilagyi et al (2008) examined data from the Hungary surveillance system for nosocomial infections between Nov 2004 and October 2006, representing 25% of Hungary hospitals. The definitions of surgical procedures and SSI, the surveillance methodology and patient risk index categories were those established by NNIS. The SSI rate amongst caesarean surgical patients was 1.31% (crude figures). Data according to risk categories is also presented. 24

Edwards et al (2009) reports data for 2006-2008 from the National healthcare Safety Network of the CDC (USA). Information on SSI rates by operative procedure are broken out by risk index categories. SRG have used the data to calculate crude SSI rates. For C Section the SSI rate is 1.8%. 27

Reilly et al report SSI rates from the Scottish Surveillance of Healthcare Associated Infection programme (SSHAIP), which is based on the CDC NNIS system methodology. 32 of 46 acute care hospitals throughout Scotland contributed data to SSHAIP for the study, which covered the period April 2002 to July 2006. For C Section the reported SSI was 1.2% without active post discharge monitoring, and 11.7% with active post discharge monitoring. SRG calculated total SSI rate for the two is 9.4%.28


Johnson et al (2005) undertook a study of SSI rates following C section in a city maternity unit with an average of 3400 births/year [appears to be Queen Mother’s Hospital, Glasow]. The study included all patients undergoing C section over a period of 35 weeks from late 2002 to the first quarter of 2003. Of 715 patients undergoing C section, 80, or 11.2%, developed an SSI. 71% were detected by post discharge surveillance. 90% of SSI diagnosed were superficial. The study refers to other papers that suggest a cost of additional inpatient care of pounds 280 per infection.4

6.4.3 Hip prosthesis SSI rate findings

Coello (2005) 3.1% of operations resulted in SSI. 74.8% superficial, 15.8% deep incisional, 9.4% organ/space.

Edwards et al (2008) undertook retrospective analysis of the medical notes of hip fracture patients in at University Hospital Nottingham, and found that, pre-discharge, 1.2% developed a deep wound infection and 1.1% developed a superficial wound infection (total 2.3%). In all cases the SSI was associated with the primary condition, rather than being a complication of a secondary procedure. Patient with peri-prosthetic fractures were excluded from the study.29

Rioux et al (2007) found SSI in 1.54% of hip prosthesis operations. The study included patient follow up for 30 days following surgery. 9

Russo et al (2006), VICNISS data between November 2002 to December 2004 give an implied crude SSI rate of 2.9% of hip prosthesis patients (calculated from data in table 2 of paper).26

Morton et al (2008) provide SSI rates by type of hip procedure and patient risk index score for surgical patients in Queensland public hospitals between 2001 and 2005. The SSI incidence rate ranges between 1.26% and 4.56%. overall mean 1.5%30

Jodra et al (2006) undertook a pairwise matched case control study of hip replacement patients between January 1 2000, and June 30, 2004 in a Madrid Spain hospital. They found a crude SSI rate of 2.2%. Only those developing SSI during hospital stay, or who were re-admitted due to SSI, were included in the statistics.31

HISWA reports contain the following data:


HISWA reports significant differences between hospitals regarding reported rates of SSI.

Szilagyi et al (2008) examined data from the Hungary surveillance system for nosocomial infections between Nov 2004 and October 2006, representing 25% of Hungary hospitals. The definitions of surgical procedures and SSI, the surveillance methodology and patient risk index categories were those established by NNIS. The SSI rate amongst hip replacement patients was 2.91% (crude figures).

Muilwijk et al (2006) estimate patient related risk for deep and superficial SSIs after all orthopaedic procedures, with special attention to primary total hip arthroplasty (THA). The study was based on PREZIES data between 1996 and 2003. For THA 0.9% of patients developed a deep SSI and 1.9% developed a superficial SSI.32

Edwards et al (2009) report reports data for 2006-2008 from the National healthcare Safety Network of the CDC. Information on SSI rates by operative procedure are broken out by risk index categories. SRG calculations have been used to calculate crude SSI rates. For Hip prothesis the SSI rate is 1.3%.

Leong et al (2006) reports data from October 1997 to September 2002 for 168 English hospitals participating in the Surgical Site Infection Surveillance Service (Previously NINSS – the Nosocomial Infection National Surveillance Service). The SSI rate for total hip replacement was 2.3%. 33


Reilly et al report SSI rates from the Scottish Surveillance of Healthcare Associated Infection programme (SSHAIP), which is based on the CDC NNIS system methodology. 32 of 46 acute care hospitals throughout Scotland contributed data to SSHAIP for the study, which covered the period April 2002 to July 2006. For hip replacement the reported SSI was 1.1% without active post discharge monitoring, and 3.1% with active post discharge monitoring. SRGs calculated total SSI rate for the two is 1.8%.

6.4.4 Knee prosthesis incidence

Coello (2005) 1.9% of operations result in SSI, 78.5% superficial, 12.4% deep incisional, 8.4% organ/space.

Rioux et al (2007) found SSI in 0.67% of knee prosthesis operations. The study included patient follow up for 30 days following surgery.

Mannien (2008) chapter 6 found that for hospitals in the PREZIES network, over a ten year period, an average decreasing trend in SSI rates of 3% per surveillance year, although this result was not statistically significant at the 95% CI.

Russo et al (2006), VICNISS data between November 2002 to December 2004 give an implied crude SSI rate of 2.8% of knee prosthesis patients (calculated from data in table 2 of paper).

Morton et al (2008) provide SSI rates by type of knee replacement and patient risk index score for surgical patients in Queensland public hospitals between 2001 and 2005. The SSI incidence rate ranges between 1.08% and 4.20%.

Edwards et al (2009) report reports data for 2006-2008 from the National healthcare Safety Network of the CDC. Information on SSI rates by operative procedure are broken out by risk index categories. SRGs calculations have been used to calculate crude SSI rates. For knee prothesis the SSI rate is 0.9%.

Leong et al (2006) reports data from October 1997 to Septembr 2002 for 168 English hospitals participating in the Surgical Site Infection Surveillance Service (Previously NINSS – the Nosocomial Infection National Surveillance Service). The SSI rate for knee prosthesis was 1.6%.

Reilly et al report SSI rates from the Scottish Surveillance of Healthcare Associated Infection programme (SSHAIP), which is based on the CDC NNIS system methodology. 32 of 46 acute care hospitals throughout Scotland contributed data to SSHAIP for the study, which covered the period April 2002 to July 2006. For knee replacement the reported SSI was 0.7% without active post discharge monitoring, and 3.1% with active post discharge monitoring. SRG’s calculated total SSI rate for the two is 1.8%.


6.4.5 CABG SSI rate findings

Coello (2005) – 4.2% of operations result in SSI, 68.8% superficial, 55.3% deep incisional, 5.9% organ/space.

Rioux et al (2007) found SSI in 2.45% of all cardiovascular surgeries. The rate for CABG is not specified, although the rate for operations on peripheral veins and arteries was 1.75%. The study included patient follow up for 30 days following surgery.

Bouza et al (2006) found an SSI rate of 2.2% amongst post-operative major heart surgery patients in ICUs during in a one-day prevalence study conducted across 42 hospitals in 13 European countries. [SRG comment - The study only appears to have covered those patients in ICU – may have only covered those that had surgery on that day. Either way, given typical delays in onset of SSI it seems a fairly high rate].34

Russo et al (2006), VICNISS data between November 2002 to December 2004 give an implied crude SSI rate of 4.3% of all coronary artery graft patients with and without donor sites (calculated from data in table 2 of paper). 26

Russo et al (2005), compares rates of SSI after CABG between VICNISS and NNIS and KISS – table reproduced below.35


Morton et al (2008) provide SSI rates by type of CABG and patient risk index score for surgical patients in Queensland public hospitals between 2001 and 2005. The SSI incidence rate ranges between 0.76% and 2.16%.30

Russo et al (2007) note that SSI rates after CABG vary between hospitals if SSI in donor sites are excluded. In addition to decreasing the SSI rate, relative rates between hospitals may change – so noting whether or not studies include donor sites is important in making comparisons. 36

Segers et al (2006) report on the impact of a risk control programme including surveillance on the incidence of surgical site infections (SSI). The study was specific to cardiothoracic surgery at the Academic Medical Centre, Amsterdam. Between 1 Jan 2001 and 31 Dec 2003, 3009 cardiothoracic surgical procedures were performed at the centre. 183 infections were diagnosed in 167 patients (5.6%)….Mean total [additional] hospital stay for SSI was 18.8 days and mean intensive care stay for SSI was 3.6 days. 21 out of 167 patients died. After starting the surveillance programme a steady decline in prevalence was observed from 8.9% to 3.9%. “This adds to the evidence that SSI after cardiothoracic surgery is a major but mainly preventable cause of morbidity and mortality.” For deep SSIs, overall mortality declined from 6.6% to 3%. The overall incidence of sternal SSI was 4.5% with 58.3% of patients developing a superficial SSI and 42.7% developing a deep SSI. Mean hospital stay for sternal SSI was 20.2 days. The incidence of leg wound infections after vein harvesting (donor site) was an SSI rate of 3.7% of patients. The average hospital stay for leg SSI was 14.6 days. A deep SSI was diagnosed in 45.3% of patients, and a superficial SSI was diagnosed in 54.7% of patients. 37

Edwards et al (2009) report reports data for 2006-2008 from the National healthcare Safety Network of the CDC. Information on SSI rates by operative


procedure are broken out by risk index categories. SRG have calculated crude SSI rates. For CABG the SSI rate is 2.8%. 27

Leong et al (2006) reports data from October 1997 to September 2002 for 168 English hospitals participating in the Surgical Site Infection Surveillance Service (Previously NINSS – the Nosocomial Infection National Surveillance Service). The SSI rate for CABG chest and donor site was 3.9% and chest site only 3.5%.33

Reilly et al report SSI rates from the Scottish Surveillance of Healthcare Associated Infection programme (SSHAIP), which is based on the CDC NNIS system methodology. 32 of 46 acute care hospitals throughout Scotland contributed data to SSHAIP for the study, which covered the period April 2002 to July 2006. For CABG the reported SSI was 3.9% without active post discharge monitoring. No hospitals undertake active post discharge monitoring of CABG patients.

6.4.6 Costs of SSI – General

Search strategy Database: Ovid MEDLINE(R) <1948 to February week 2 2011> Search Strategy **Also run in the Cochrane Library: -------------------------------------------------------------------------------- 1 Surgical Wound Infection/ (24671) 2 Hip Prosthesis/mi (91) 3 knee prosthesis/mi (73) 4 prosthesis related infections/ (5710) 5 exp Caesarean Section/ (30340) 6 Knee Prosthesis/ (7058) 7 hip prosthesis/ (15901) 8 coronary artery bypass graft*.mp. (18589) 9 staphylococcal infections/ (39172) 10 Cross Infection/ (39070) 11 (5 or 6 or 7 or 8) and (9 or 10) (456) 12 surgical site infection*.mp. (1856) 13 *Surgical Wound Infection/ or *Hip Prosthesis/mi or *knee prosthesis/mi or *prosthesis related infections/ or 11 or 12 (19191) 14 "cost of illness"/ (13507) 15 hospital costs/ (6287) 16 Employer Health Costs/ (1025) 17 actuarial analysis/ (6559) 18 life tables/ (5699) 19 quality adjusted life years/ (4760) 20 health care costs/ (20472) 21 exp "Costs and Cost Analysis"/ (153484) 22 13 and (*"cost of illness"/ or *hospital costs/ or *Employer Health Costs/ or *actuarial analysis/ or *life tables/ or *quality adjusted life years/ or *health care costs/ or exp *"Costs and Cost Analysis"/) (71) 23 *surgical wound infection/ec (87) 24 22 or 23 (123) 25 limit 24 to (english language and yr="2006 -Current") (52)


Broex 2009 review 16 studies reporting on increased costs due to SSI and conclude that “a patient with an SSI costs approximately twice the amount of a patient without an infection…The LOS has more than doubled on average (increase by a mean of 176%, median 173%) a greater increase than that of costs, which suggests that the additional LOS is only partially reflected in the additional costs of SSI. 38

Sparling et al (2007) estimate that for pediatric patients developing preventable SSI, the increased LOS was on average 10.6 days and costs were increased by $27 288. 39

Alfonso (2007) estimated that 9.02% of patients developed SSI, stays were prolonged on average by 14 days, with resources being used more intensively and for longer periods than in controls. Excess hospital costs were $10,232 per patient, of which 37% corresponded to prolonged stays. Health costs only accounted for 10% of overall costs; $97,433 per patient including indirect social costs. The study used a cost of illness approach. The finding of excess hospital costs of $10,232 were higher than most other studies. It is not entirely clear why, although the authors seem to imply that their study is wider ranging than most. It is noted that the study was only undertaken at one hospital, so behaviours particular to that hospital may impact on the results. 40

Defez (2008) looked at the costs of a range of nosocomial infections in a French university hospital. Costs resulting from laboratory tests, radiology, surgery, and exploratory examinations, and antimicrobial agents were estimated at Euro 1814 for a surgical site infection.41

Yasunga et al (2007) report on 15 studies of the cost of SSIs. Average total costs in the 8 weeks post discharge were $3330 higher in the SSI patients. The average cost of a deep post cardiac surgical infection was $18938. 16

Walter et al (2011) assess the costs of additional healthcare due to SSIs for Visceral, Vascular and Traumatology patients at Basel University Hospital in Switzerland between 1 January 2000 and 31 December 2001, selecting matched case controls for each patient developing an SSI. See tables below – focus on hospital costs.


6.4.7 Costs of SSI - Hip & knee prosthesis

Coello (2005) LOS days for hip patients without SSI, and additional LOS with SSI and cost in pounds attributable to each SSI: 11.1, 11.5, £3342. Adjusted extra postoperative LOS and extra cost of hospitalisation by type of surgical site infection; superficial incisional 8.9 , deep incisional and organ/space 22.8 , extra cost superficial incisional £2586, extra cost deep incisional and organ/space £6626. 2 Coello (2005) LOS days for Knee patients without SSI, and additional LOS with SSI and cost in pounds attributable to each SSI:10.3,10.9, £3168. Adjusted extra postoperative LOS and extra cost of hospitalisation by type of surgical site infection; superficial incisional 8.6, deep incisional and organ/space 21.1, extra cost superficial incisional £2499 extra cost deep incisional and organ/space £6132

Edwards (2008), includes information on costs of SSI related to hip fracture surgery. Not sure whether all procedures included are relevant to the “hip prosthesis” intended for surveillance under this study and peri-prosthetic fractures were excluded. The mean hospital costs of treating hip fractures were estimated at £8978.56 for non-SSI and £25940.44 for patients with an SSI. A breakdown of the source of the costs is included in the study. 29 Jodra et al (2006) undertook a pairwise matched case control study of hip replacement patients between January 1 2000, and June 30, 2004 in a Madrid Spain hospital. The median excess LOS attributable to SSI was 32.5 days, whereas the median prolonged postoperative stay due to SSI was 31 days. Deep-wound SSI was the type that prolonged hospital stay the most (up to 49 days). Of the patients who


developed an SSI, 4 required revision surgery, for an SSI-related morbidity rate of 14.3%. 31 Szilagyi et al (2008) examined data from the Hungary surveillance system for nosocomial infections between Nov 2004 and October 2006, representing 25% of Hungary hospitals. The definitions of surgical procedures and SSI, the surveillance methodology and patient risk index categories were those established by NNIS. Those persons developing SSI after hip replacement experienced on average an additional 6 days of postoperative hospital stay. 24

6.4.8 Caesareans cost of SSI

Olsen (2010) cost of surgical site infections after caesarean delivery estimated at $3,400 - $3,700. 42 Olsen (2010) (paper B) attributable total costs of SSI following low transverse caesarean section vary according to calculation method. $US2852 using matched pairs or $US3529 using generalised least squares, relative to patient not developing SSI. 25

Szilagyi et al (2008) examined data from the Hungary surveillance system for nosocomial infections between Nov 2004 and October 2006, representing 25% of Hungary hospitals. The definitions of surgical procedures and SSI, the surveillance methodology and patient risk index categories were those established by NNIS. Those persons developing SSI after caesarean experienced on average an additional 7 days of postoperative hospital stay. 24

6.4.9 CABG – Cost of SSI

Coello (2005) LOS days for patients without SSI, and additional LOS with SSI and cost in pounds attributable to each SSI: 7.4, 13.4, £3894. Adjusted extra postoperative LOS and extra cost of hospitalisation by type of surgical site infection; superficial incisional 10.8, deep incisional and organ/space 22.1 , extra cost superficial incisional £3138 extra cost deep incisional and organ/space £6422. Segers et al (2006) report on the impact of a risk control programme including surveillance on the incidence of surgical site infections (SSI). The study was specific to cardiothoracic surgery at the Academic Medical Centre, Amsterdam. Between 1 Jan 2001 and 31 Dec 2003, 3009 cardiothoracic surgical procedures were performed at the centre. Mean total [additional] hospital stay for SSI was 18.8 days and mean intensive care stay for SSI was 3.6 days. 21 out of 167 patients died. Mean hospital stay for sternal SSI was 20.2 days. The average hospital stay for leg SSI was 14.6 days.


6.4.10 Studies estimating reduction due to surveillance

Search Strategy Database: Ovid MEDLINE(R) <1948 to February week 2 2011> and Cochrane Library Search Strategy: -------------------------------------------------------------------------------- 1 exp Surgical Wound Infection/ (24671) 2 exp *Surgical Wound Infection/ and surveill*.mp. (695) 3 (surg* adj5 ((wound or site) adj5 surveill*)).mp. (278) 4 Prosthesis-Related Infections/ and surveill*.mp. [mp=protocol supplementary concept, rare disease supplementary concept, title, original title, abstract, name of substance word, subject heading word, unique identifier] (64) 5 (hip prosthesis/mi or knee prosthesis/mi) and surveill*.mp. (1) 6 staphylococcal infections/ and surveill*.mp. and (caesarean or prosthe* or bypass graft*).mp. [mp=protocol supplementary concept, rare disease supplementary concept, title, original title, abstract, name of substance word, subject heading word, unique identifier] (32) 7 2 or 3 or 4 or 5 or 6 (794) 8 exp infection control/ or cross infection/pc or staphyloccocal infections/pc or surgical wound infection/pc or risk management/ (73752) 9 7 and 8 (403) 10 limit 9 to (english language and yr="2006 -Current") (133)

Database: Ovid MEDLINE(R) <1948 to February week 2 2011> Search Strategy: -------------------------------------------------------------------------------- 1 (reduc* or decreas*) adj7 infection* adj7 surveill*).mp. [mp=protocol supplementary concept, rare disease supplementary concept, title, original title, abstract, name of substance word, subject heading word, unique identifier] (127) 2 limit 1 to (english language and yr="2006 -Current") (48) 3 2 and (surg* or nosocom* or operation*).mp. [mp=protocol supplementary concept, rare disease supplementary concept, title, original title, abstract, name of substance word, subject heading word, unique identifier] (29)

Findings

Rioux et al (2007) looked at the results from a six year surveillance system amongst volunteer surgical wards in hospitals from Northern France. Surgical wards did not necessarily participate in the study every year. Patients were followed for 30 days following surgery. Over six years the crude SSI incidence decreased from 3.8% to 1.7% and the NNIS-O5

5 National Nosocomial Infections Surveillance system (NNIS) is a risk index of likelihood of patient developing an SSI.

adjusted SSI rate fell from 2% to 1%. The authors conclude that an active surveillance system striving for benchmark through a network is an effective strategy to reduce SSI incidence. 54.4% of SSIs were diagnosed in patients during the hospital stay, pointing to the large proportion of SSIs that do not become apparent until after discharge. The mean time between surgery and diagnosis was 11.7 days.


SSIs were superficial in 64.3% of cases, and deep or organ/space in 35.7%. 21.6% of cases required re-operation. In contrast to most other studies individual data was not returned to surgeons. However, each member of the surgical team was meant to have knowledge of the surgical unit’s results. The network promoted benchmarking and inter-ward and inter-hospital comparison. Each local surgery team had the opportunity to compare their results with each other, and to measure it’s own performance. Only a small set of wards participated in each of the six years of the study. The study found that a regular or minimal (at least twice) participation in the surveillance network could impact on the SSI risk reduction. 9

Astagneau & L’Heriteau (2010) “The reason for such SSI risk reduction and the impact of the surveillance process on healthcare quality improvement are not so easy to explain. Few studies correlate quality of care indicators and temporal trends in SSI rates.” “Although demonstrating the direct link with the technical performance of the surgeon is hard, it is likely that performance feedback increases the compliance of the surgical team to prevention measures. Moreover, increasing awareness about the infection risk may have an influence on reducing malpractices of surgeons and their team, especially when each infectious event recorded by the surveillance is analysed using root cause analysis methods.”43

Geubbels (2006) – concludes that surveillance, supported by participation in a surveillance network reduced the risk of SSI in surgical patients registered in the Dutch surveillance network PREZIES. Risk of infection was reduced for patients who had an operation during the fourth surveillance year. The incidence of SSI remained relatively stable at around 4.3% in the first three surveillance years and then dropped to 3.3% in the fourth year and further down to 1.8% in the last surveillance year. Paper also has risk ratio analysis.7

Brandt (2006), looked at 130 surgical departments of German hospitals participating in the Krankenhaus Infektions Surveillance System (KISS). Compared with the surveillance year one, the SSI risk decreased in year 2 (odds ration 0.84) and in year 3 (odds ratio 0.75) and there was no change in year 4. The study concluded that the SSI incidence was reduced by one quarter as a result of the surveillance-induced infection control efforts, which indicates the usefulness of a voluntary surveillance system. The SSI rate reduced as follows (unadjusted data), note post discharge monitoring in KISS is “strongly recommended” – so not clear included consistently. 6


Table 28

Year 1 Year 2 Year 3 Year 4 Caesarean section 2.37 2.06 1.66 1.25 CABG 3.56 2.08 2.02 2.35 Hip prosthesis arthroplasty 2.15 1.94 1.64 1.61 Knee prosthesis arthroplasty 1.01 1.27 0.74 0.94

Astagneau et al (2009) estimate the reduction in surgical site infection incidence through the French ISO-RAISIN surveillance system. They evaluated the impact of an eight year national SSI surveillance system, finding that “Both crude and NNIS-0 SSI incidence decreased significantly by 38% and 32%, respectively, between 1999 and 2006. The decrease in SSI incidence was not linear, and was mainly apparent in the first three years, followed thereafter by fluctuating decrease from 2002 to 2006. A similar temporal trend was observed for relative risk estimated in the multivariate analysis showing a reduction by 30% between 1999 and 2006. The proportion of superficial v deep incisional or organ space SSI decreased over the study period (61.0% in 1999 v 54.5% in 2006)” Found a significant reduction over the period in reported rates of SSI for Caesaran section (-56%) and or hip prosthesis (-36%) patients.

Carlet et al (2009) report on the French ISO-RASIN programme, looking at surgical site infection rates between 1999 and 2005. They found that SSI rates declined by 25% over the 6 year period.

Gastmeier et al (2006) “The aim of this study was to investigate whether participation in the German national NI surveillance system [KISS] resulted in reduced rates of NIS…..Data were collected from January 1997 until December 2003. Only institutions that had participated in KISS for at least 36 months were considered for analysis. Data from the first 12 months of surveillance were compared with data from the second and third 12-month periods. One hundred and fifty ICUs and 133 surgical departments fulfilled the inclusion criteria. ….The average SSI rate in the surgical inpatients was 1.6 per 100 operations in their first year of participation. Comparing the infection rates in the third year with the first year…..The corresponding RR for SSI was 0.72 [95% CI0.64-0.80]. Participation in KISS was associated with a significant reduction in these three NI rates.

Mannien (2008) chapter 6 finds that for hospitals in the PREZIES network over a ten year period the rate of SSI fell by an average of 6% per surveillance year (statistically significant at 95% CI), being a 60% decrease over ten years.

Segers et al (2006) report on the impact of a risk control programme including surveillance on the incidence of surgical site infections (SSI). After starting the


surveillance programme a steady decline in prevalence was observed from 8.9% to 3.9%. “This adds to the evidence that SSI after cardiothoracic surgery is a major but mainly preventable cause of morbidity and mortality.” For deep SSIs, overall mortality declined from 6.6% to 3%.


6.4.11 Summary tables

Table 29: Baseline infection rates – Caesarean section

Study ref & brief description Procedure type Time period SSI rate Comment Olsen et al 2010 “Attributable costs…” case control study on 491 women who underwent low transverse caesarean delivery - administrative claims data (no Post discharge Survey)

Low transverse caesarean delivery

1999 - 2001 5% “mainly superficial – but not enumerated)

Barnes-Jewish Hospital, a tertiary care hospital in Saint Louis, Missouri.

Rioux et al (2007) For study design see above – includes post discharge survey

Caesarean section 1988-2003 3.08% The study included patient follow up for 30 days following surgery.

Astagneau et al (2009) Study design – see above

Caesarean section 1999-2006 2.1% (preintervention)

Found that reported rates of SSI for Caesarean section decreased by 56% post surveillance implementation.

Russo et al (2006) Reports findings from the VICNISS surveillance programme

Caesarean section November 2002 - December 2004

2.1% (calculated from data in table 2 of paper). Excludes post discharge survey.

Barwolff et al (2006) used KISS data to assess whether surveillance and feedback of healthcare associated infections could reduce the infection rate after caesarean delivery (CD) in 26 Departments. Post discharge surveillance is not performed routinely as part of the KISS, but SSIs that become evident after discharge are also included.

Caesarean delivery 1997 - 2003 2.4% preintervention. 1.6% postintervention

17405 CD procedures were performed and 331 SSIs were recorded (1.9%) over 3 years. Excl post discharge survey.

Szilagyi et al (2008) examined data from the Hungary surveillance system for nosocomial infections between Nov 2004 and October 2006, representing 25% of Hungary’s hospitals. NNIS definitions and methods.

Caesarean section Nov 2004 – October 2006

1.31% The SSI rate amongst surgical patients was overall 2.27%. Excludes post discharge survey.

Edwards et al (2009) reports data for 2006-2008 from the National healthcare Safety Network of the CDC, for the device associated and procedure associated modules of the National Healthcare Safety Network.

Caesarean section (data for other procedures also presented)

2006-2008 1.8% Crude SSI rate calculated by Sapere from the data presented in the paper

Johnson et al (2005) a study of SSI rates following Caesarean section in a city maternity unit with an average of 3400 births/year [appears to be Queen Mother’s Hospital, Glasgow]. The study included all patients undergoing caesarean section over a period of 35 weeks

Caesarean section late 2002 to first quarter 2003.

11.2% Includes post discharge monitoring -71% were detected by post discharge surveillance. 90% of SSI diagnosed were superficial.


Table 29: Baseline infection rates – Caesarean section

Study ref & brief description Procedure type Time period SSI rate Comment Johnson et al (2005) a study of SSI rates following Caesarean section in a city maternity unit with an average of 3400 births/year [appears to be Queen Mother’s Hospital, Glasgow]. The study included all patients undergoing caesarean section over a period of 35 weeks

Caesarean section late 2002 to first quarter 2003.

11.2% Includes post discharge monitoring -71% were detected by post discharge surveillance. 90% of SSI diagnosed were superficial.

Note: shaded studies were not included in the summary as they used post discharge surveys.

Table 30: Baseline infection rates – hip and knee procedures

Study ref & brief description Procedure type Time period SSI rate Comment Coello (2005) reports on Nosocomial Infection National Surveillance Service (NINSS) data. Only SSIs diagnosed during the hospital admission for the operation were included.

Hip prosthesis 1997 and 2001 3.1% 74.8% superficial, 15.8% deep incisional, 9.4% organ/space

Knee prothesis 1997 and 2001

1.9% 78.5% superficial, 12.4% deep incisional, 8.4% organ/space

Edwards et al (2008) retrospective analysis of the medical notes of hip fracture patients in at University Hospital Nottingham. Patient with peri-prosthetic fractures were excluded from the study.

Hip fracture patients treated surgically

1999 - 2004 2.3% Pre-discharge, 1.2% developed a deep wound infection and 1.1% developed a superficial wound infection.

Russo et al (2006), VICNISS data. For study design see above

Hip prothesis 2002 - 2004 2.9% calculated from data in table 2 of paper Knee prothesis 2002 - 2004 2.8% calculated from data in table 2 of paper.

Morton et al (2008) provide SSI rates by type of hip procedure and patient risk index score for surgical patients in Queensland public hospitals. Appears to be in hospital surveillance only.

Partial or total hip replacement, or revision

2001 - 2005. 1.26% - 4.56% Rate varies depending on procedure and risk score

Total knee replacement, Revision knee replacement

2001 - 2005. 1.08% - 4.2%

Jodra et al (2006) - pairwise matched case control study of hip replacement patients in a Madrid Spain hospital.

Hip replacement 2000 - 2004 2.2%. Only those developing SSI during hospital stay, or who were re-admitted due to SSI, were included in the statistics.

Szilagyi et al (2008) examined data from the Hungary surveillance system for nosocomial infections, representing

Hip replacement 2004 - 2006 2.91%

The SSI rate amongst surgical patients was overall 2.27%.



Study ref & brief description Procedure type Time period SSI rate Comment 25% of Hungary’s hospitals. NNIS definitions and methods. Muilwijk et al (2006) estimate patient related risk for deep and superficial SSIs after all orthopaedic procedures, with special attention to primary total hip arthroplasty (THA). The study was based on PREZIES data.

Total hip arthroplasty Between 1996 and 2003.

2.8% Included patients who underwent active post discharge surveillance for 30 days or for 1 year post implant. 0.9% deep SSI and 1.9% superficial. Post discharge surveillance in PREZIE does not include surveys, but does include outpt f/up.

Edwards et al (2009) report data for 2006-2008 from the National healthcare Safety Network of the CDC,

Hip prosthesis 2006-2008 1.3% Information on SSI rates by operative procedure are broken out by risk index categories. Our calculations give a crude SSI rate for Hip prothesis of 1.3%.

Edwards et al (2009) report reports data from the National healthcare Safety Network of the CDC.

Knee prothesis 2006-2008 0.9% Information on SSI rates by operative procedure are broken out by risk index categories. Our calculations suggest a crude SSI rate for knee prothesis of 0.9%.

Leong et al (2006) reports data for 168 English hospitals participating in the Surgical Site Infection Surveillance Service (Previously NINSS – the Nosocomial Infection National Surveillance Service).

Total hip replacement 1997 - 2002 2.3%. Appears to be inpatient SSI development only.

Knee prothesis 1997 - 2002 1.6%. Appears to be inpatient SSI development only

Reilly et al (no year) report SSI rates from the Scottish Surveillance of Healthcare Associated Infection programme (SSHAIP), which is based on the CDC NNIS system methodology. 32 of 46 acute care hospitals throughout Scotland contributed data to SSHAIP for the study.

Hip replacement 2002 - 2006. 1.8%. Reported SSI was 1.1% without active post discharge monitoring, and 3.1% with active post discharge monitoring. Combined rate calculated by Sapere.

Knee prothesis 2002 - July 2006.

0.7% For knee replacement the reported SSI was 0.7% without active post discharge monitoring, and 3.1% with active post discharge monitoring. Our calculated total SSI rate for the two is 1.8%.

Kurtz et al 2010, reviewed medicare administrative data set to identify infections post knee arthroplasty

Total knee arthroplasty 1997 - 2006 1.55% 1.55% in first 2 years post surgery – another 0.46% in next 8 years.



Study ref & brief description Procedure type Time period SSI rate Comment Rioux et al (2007). For study design, see above

knee prosthesis Hip joint prothesis

1988 – 2003 1988-2003

0.67% 1.54%.

The study included patient follow up for 30 days following surgery – but only for readmissions.

Hospital Infection Surveillance Western Australia Knee procedures 2005-2009 1.71%. In 2008-09 46% were deep/organ space infection

Hip arthroplasties 2005-2009 1.77%

In 2008-09 52% were deep/organ space infections

Table 31: Baseline infection rates - CABG

Study ref & brief description Procedure type Time period

SSI rate Comment

Coello (2005) reports on Nosocomial Infection National Surveillance Service (NINSS) data and estimates costs of these infections based on cost estimates from other studies

Coronary artery bypass graft 1997 and 2001

4.2% Only SSIs diagnosed during the hospital admission for the operation were included. 68.8% superficial, 25.3% deep incisional, 5.9% organ/space

Rioux et al (2007). For study design see above

Cardiovascular surgery (not specific to CABG)

1988-2003 2.45% The rate for CABG is not specified.

Bouza et al (2006). A one-day prevalence study amongst post-operative major heart surgery patients in ICUs conducted across 42 hospitals in 13 European countries.

Major heart surgery ? 2005 2.2% The study only appears to have covered those patients in ICU.

Russo et al (2006), Reports on VICNISS data Coronary artery grafts 2002 - 2004

4.3% Calculated from data in table 2 of paper).

Morton et al (2008) provide SSI rates by type of CABG and patient risk index score for surgical patients in Queensland public hospitals.

CABG with graft, sternal wound; CABG graft wound; and CABG without graft, sternal wound

2001 - 2005

0.76% - 2.16% Graft wound: 1.47 – 2.16 Sternal wound: 0.76 - 1.27

Appears to be inhospital surveillance only. The SSI incidence rate varies depending on procedure and risk score.


Table 31: Baseline infection rates - CABG

Study ref & brief description Procedure type Time period

SSI rate Comment

Segers et al (2006) report on the impact of a risk control programme including surveillance on the incidence of surgical site infections (SSI). The study was specific to cardiothoracic surgery at the Academic Medical Centre, Amsterdam. 3009 cardiothoracic surgical procedures were reviewed. Infections were detected by means of an SSI database, registrations of surgical procedures and wound cultures.

Cardiothoracic surgical procedures.

2001 2003, 8.9% preintervention

After starting the surveillance programme a steady decline in prevalence was observed from 8.9% to 3.9%. For deep SSIs, overall mortality declined from 6.6% to 3%.

Sternal SSI 4.5% with 58.3% of patients developing a superficial SSI and 42.7% developing a deep SSI.

Leg wound (donor site) SSI in cardiothoracic surgery patients

3.7%. A deep SSI was diagnosed in 45.3% of patients, and a superficial SSI was diagnosed in 54.7% of patients. Infections were detected by means of an SSI database, registrations of surgical procedures and wound cultures.

Edwards et al (2009) report reports data from the National healthcare Safety Network of the CDC. Information on SSI rates by operative procedure are broken out by risk index categories

Coronary bypass with chest and donor incision; and coronary bypass graft with chest incision

2006-2008 2.8%. Data on the type of SSI for CABG is also presented broken out by risk index (could be aggregated). (Our calculations – crude rate)

Leong et al (2006) reports data for 168 English hospitals participating in the Surgical Site Infection Surveillance Service (Previously NINSS – the Nosocomial Infection National Surveillance Service).

CABG – chest and donor site; and CABG chest only

1997 2002 donor site 3.9% chest site 3.5%.

Appears to be inpatient SSI development only.

Reilly et al (no year) report SSI rates from the Scottish Surveillance of Healthcare Associated Infection programme (SSHAIP), which is based on the CDC NNIS system methodology. 32 of 46 acute care hospitals throughout Scotland contributed data to SSHAIP for the study, which covered the period April 2002 to July 2006.

CABG 2002 - July 2006.

3.9%. No hospitals undertake active post discharge monitoring of CABG patients.


Table 32: Studies on general SSI rates - summary

Study ref & brief description SSI rate Broex et al 2009 – review of studies 2.5 Gastmierer 1.6 Roux 3.8 Mannien 2007 – PREZIES data 3.5 Mannien 2007 – KISS data 2.2 Mean 2.72 Std dev 0.91

Table 33: Cost of surgical site infection

Study ref & brief description Procedure type Time period Estimated cost of SSIs Broex 2009, review 16 studies reporting on increased costs due to SSI. Costs were translated to $US using purchasing power parity. 38

Range of procedures N/a Conclude that “a patient with an SSI costs approximately twice the amount of a patient without an infection…The LOS has more than doubled on average (increase by a mean of 176%, median 173%) a greater increase than that of costs, which suggests that the additional LOS is only partially reflected in the additional costs of SSI.

Alfonso (2007) Prospective study of case series of patients who have undergone major surgical treatment. Those with SSI were compared with controls. CDC definitions were followed. Study was performed in a general tertiary hospital in Valencia Spain, with data gathered between January 1 2001 and June 30 2005. Overall costs and including indirect costs were estimated. Cost of illness methodology with human capital theory (wage data from interview) and years of productivity life lost.

Major surgical Date of costings uncertain. Jan 2001 – June 2005

Estimated that 9.02% of patients developed SSI, stays were prolonged on average by 14 days, with resources being used more intensively and for longer periods than in controls. Excess hospital costs were $10,232 per patient, of which 37% corresponded to prolonged stays. Health costs only accounted for 10% of overall costs; $97,433 per patient including indirect social costs.

Defez (2008) looked at the costs of a range of nosocomial infections in a French university

Hospitalised due to surgical site infection

May 2001 to January 2003.

Costs resulting from laboratory tests, radiology, surgery, and exploratory examinations, and antimicrobial agents were



Study ref & brief description Procedure type Time period Estimated cost of SSIs hospital. From patients hospitalised with an infection, Thirty patients were randomly chosen for the type of infection, and matched against non-infected patients

Date of costings uncertain

estimated at Euro 1814 for a surgical site infection.

Walter et al (2011) assess the costs of additional healthcare due to SSIs for Visceral, Vascular and Traumatology patients at Basel University Hospital in Switzerland between 1 January 2000 and 31 December 2001, selecting matched case controls for each patient developing an SSI.

Vascular January 2000 and 31 December 2001

Hospital costs in swiss francs were on average (mean) 19,638 higher for patients with SSI

Edwards, 2008, 29, includes information on costs of SSI related to hip fracture surgery.

Hip prosthesis The mean hospital costs of treating hip fractures were estimated at £8978.56 for non-SSI and £25940.44 for patients with an SSI.

al (2006) undertook a pairwise matched case control study of hip replacement patients between January 1 2000, and June 30, 2004 in a Madrid Spain hospital.

Hip prosthesis January 1 2000, and June 30, 2004

The median excess LOS attributable to SSI was 32.5 days, whereas the median prolonged postoperative stay due to SSI was 31 days. Deep-wound SSI was the type that prolonged hospital stay the most (up to 49 days). Of the patients who developed an SSI, 4 required revision surgery, for an SSI-related morbidity rate of 14.3%.

Szilagyi et al (2008) examined data from the Hungary surveillance system for nosocomial infections between Nov 2004 and October 2006, representing 25% of Hungary hospitals. The definitions of surgical procedures and SSI, the surveillance methodology and patient risk index categories were those established by NNIS.

Hip prothesis Nov 2004 and October 2006

Those persons developing SSI after hip replacement experienced on average an additional 6 days of postoperative hospital stay.

Caesarean sections Nov 2004 and October 2006

Those persons developing SSI after caesarean experienced on average an additional 7 days of postoperative hospital stay.

Coello (2005)

Knee prothesis Mean LOS days for patient without SSI, extra days LOS with SSI and cost in pounds attributable to each SSI: 10.3, 10.9, £3168. Adjusted extra postoperative LOS and extra cost of hospitalisation by type of surgical site infection; superficial incisional 8.6, deep incisional and organ/space 21.1, extra cost superficial incisional £2499 extra cost deep incisional



Study ref & brief description Procedure type Time period Estimated cost of SSIs and organ/space £6132

CABG Mean LOS days for patients without SSI, additional LOS of those with SSI and cost in pounds attributable to each SSI: 7.4, 13.4, £3894. Adjusted extra postoperative LOS and extra cost of hospitalisation by type of surgical site infection; superficial incisional 10.8, deep incisional and organ/space 22.1 , extra cost superficial incisional £3138 extra cost deep incisional and organ/space £6422

Hip prosthesis Mean LOS days for patient without SSI, extra days LOS with SSI, and cost in pounds attributable to each SSI: 11.1, 11.5, £3342. Adjusted extra postoperative LOS and extra cost of hospitalisation by type of surgical site infection; superficial incisional 8.9 , deep incisional and organ/space 22.8 , extra cost superficial incisional £2586 extra cost deep incisional and organ/space £6626.

Olsen et al 2010, case control study 491 women. 42

Caesarean sections 2008 Cost of surgical site infections after caesarean delivery estimated at $3,400 - $3,700. Increase in ALOS of 4.5 days – mainly superficial infections

Olsen et al 2010 25 (paper B)

Low transverse caesarean

2008 Attributable total costs of SSI following low transverse caesarean section vary according to calculation method. $US2852 using matched pairs or $US3529 using generalised least squares, relative to patient not developing SSI.

Upton et al, 2005 [add to endnote] NZ (ADHB) Matched case control – 18 patients – patients with deep infection at the sterna site.

Cardiac surgery 2002 - 2003 Patients with S. aureus had a significantly higher LOS – extra 32 days. And extra cost of $NZ45,677 per pt.

Segers et al (2006) Cardiotharic surgery 2001 - 2003 Mean total [additional] hospital stay for SSI was 18.8 days and mean intensive care stay for SSI was 3.6 days.

Sternal cardio surgery Mean extra hospital stay for sternal SSI was 20.2 days. Donor site – leg wound on cardio patients

Mean extra hospital stay for leg SSI was 14.6 days


Table 34 Summary LOS impact

Other Hips/knees Caesars CABG:

Szilagyi et al 6 7

Jodra et al

32

Coello

11.5

13.4

Coello

10.9

20

Alfonso 14

14.6

VICNISS

27

Upton

32

Segers

18.8

Olsen

4.5 Mean 14 17.5 5.8 19.8

St dev

11.3 1.8 7.4

median 14 11.5 5.8 18.8


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Documents

Cost benefit analysis of the proposed national surgical