Improving the Value of Screening For Macular

Oedema usingSurrogate Photographic

Markers

Dr John Olson

NHS Grampian

Improving The Economic Value Of Photographic Screening For Optical Coherence Tomography

Detectable Macular Oedema – A Prospective Multicentre, United Kingdom Study

• Olson J, Sharp P , Goatman K, Prescott G, Scotland G, Fleming A, Philip S, Santiago C, Borooah S, Broadbent D, Chong V, Dodson P, Harding S, Leese G, Styles C, Swa K, Wharton H

• Health Technol Assess, Vol 17,, May- June 2013, In Press

A Success Story?

• Systematic screening programme for diabetic retinopathy

Missing the target?

• The health-economic case is based on the detection of people with, or at risk of– proliferative diabetic

retinopathy– before they develop

complications• Vitreous haemorrhage• Traction retinal detachment

• But 90% of referrals are for ? diabetic macular oedema

Why?

• Retinal photographs are not discriminatory for proliferative retinopathy or its precursors

• Other things may be present– e.g. diabetic “maculopathy”– We have to manage these findings

How did we get there?

• Retinopathy grades based on ETDRS

• Maculopathy grades basedon

…(GOBSAT)

Different management

New Vessels Oedema

Definitive treatment Indefinite treatment

Management independent of visual acuity

Management depended on visual acuity

2 D red structure 3 D transparent elevation

Few false +ves Many false +ves

What did ISMO question?

• Can we do it better?

• What will it cost?

• What will it mean?

The Answers In Short- Can Grading Schemes do it better ?

• Computer says nah

The Answers In Short- Can OCT do it better ?

• Yes• Increases the

specificity of referrals• With no loss of

sensitivity

The Answers-What will it cost?

• Less• If you use OCT • Whatever grading

strategy you use• Saves you money

The Answers- What will it mean?

Study Highlights

© 2008 Google-Imagery © 2008 TerraMetrics

Aberdeen

Dundee

Edinburgh

Liverpool

Birmingham

Oxford

Study centres

Aberdeen

Birmingham

Dundee

Edinburgh

Glasgow

Liverpool

Oxford

Glasgow

Every day practice

Aberdeen

Dundee

Edinburgh

Liverpool

Birmingham

Oxford

Glasgow

3450 Subjects

• Photographic signs of diabetic retinopathy– exudates ≤ 2DDr– blot haemorrhages ≤ 1DDr– dot haemorrhages/microaneurysms ≤ 1DDr

• Each subject had photography and optical coherence tomography on both eyes, where possible.

Patient Characteristics

• Median age 60

• 60.7% male

• 85.4% Caucasian

• 77.4% type 2 diabetes

370 Excluded (10.5%)

• 6 years older

• Female

• Asian/ Black

• Zeiss Stratus

• Topcon OCT 1000

Lesion Distribution

Expected % Recruited %

Ma/dot only 69.8 40.3

Blot no exudate 8.6 8.4

Exudate 21.6 20.4

No Ma/dot/blot/exudate ≤ 1DDr

28.1

Definition of Macular Oedema

• Central ETDRS region thickness > 250µm

• OR any of 5 inner regions > 300µm

• AND visible intraretinal cyst/ area of subretinal fluid

Prevalence of oedema

• 7.7% of study population

• Prevalence differed greatly by centre– 3.7% to 12.2%

• Prevalence differed greatly by scanner– 4.5% to 11.8%

Relationship to Centre

• Aberdeen 12.0%• Birmingham 3.7%• Dundee 12.2%• Edinburgh 6.4%• Liverpool 2.9%• Dunfermline 4.4%• Oxford 7.7%

All scanners are equal, but some scanners are more equal than others

• Zeiss Stratus– 4.5%

• Topcon OCT1000– 6.5%

• Heidelberg Spectralis– 8.7%

• Zeiss Cirrus– 11.8%

Relationship to patient features

• Older age– 68yrs cf 60

• Caucasian– 8.4% cf 3-4%

• Type 2 diabetes– 8.7% cf 3.9%

• Poorer vision– 5x more likely– If VA ≤ 6/9

• BUT NOT– Sex, glitazone, amblyopia

Relationship to Lesions

R Eye % L Eye %

No lesions

0.8 0.6

Ma/dot only

2.2 2.3

Blot no Exudate

10.2 11.2

Exudate 12.5 11.2

Other 1.1 1.1

Can we do any better?

• Three Grading Strategies Examined– Manual grading

• Presence/ absence of features• SDRGS 2007

– Computer-assisted manual annotation• All individual lesions ≤ 2DDr

– Fully automated annotation grading• Three versions

– Automated image analysis– +VA

– +VA + Age+ Type DM + Sex

Manual Grading (features)

Manual Grading (features)

• Scotland– 59.5% sensitivity– 79.0% specificity

• England– 72.6% sensitivity– 66.8% specificity

• England plus– 73.3% sensitivity– 70.9% specificity

Computer Assisted, Manual Annotation, Grading• Best for sensitivity &

specificity• Time-consuming

procedure • Unlikely to be

considered for routine screening practice

In Years To Come

Marvin the Manically Depressed Autograder

""I think you ought to I think you ought to know…. I'm feeling know…. I'm feeling very very depressed ......noboddepressed ......nobody likes mey likes me""

DRS in Scotland 2012

What will it cost?

• Cost per screen £33.13• Cost per OCT screen £31.96• Total cost for ?oedema £65.09

• Cost of attending ophthalmology £90.00

• (Cost of Slit lamp within DRS £27.29)

TABLE 30 Screening and referral cost per true case of macular oedema detected for 3,170 patients; Adjusted for expected frequency of different patient categories and based on Scottish screening and referral costs

* Reference strategy; a figures in table based on assumption that fully automated grading can be implemented at zero net increase in grading costs;++ Represents a cost saving per case missed relative to the reference strategy; d strategy more costly and less effective than an alternative strategy (dominated)

What does it mean?

• At present we spend £13,750,000 a year – 250,000 people @ £55– Screening + 1st visit to

ophthalmology– £2,337,500 on ? M2

• If we do nothing, other than introduce OCT into the screening pathway

• we save money

Should we grade differently?

Current Scottish Criteria + OCT is the most cost effective of all strategies

What if we do nothing? 20 year “M2” Markov Model• Only 5.6% of M2 at risk of visual loss• Repetitive nature of screening

– 12% of non-referred MO modelled to progress at 12 months cf 5% of referred (laser Rx)

• More sensitive strategies– More OCTs, more referrals

• Bilateral incidence 12%– QALY determined by VA in better seeing eye

• Additional cost per QALY going to strategy 16– £882,307 at 5 years– £353,927 at 20 years– (£20-30,00 UK threshold for “cost-effectiveness)

What should we do?

Cost-effectiveness acceptability curves for the alternative strategies based on a 20 year time horizon and using quality adjusted life years as the measure of effect

How should we manage M2s?Is this the answer?

• Photos graded as M2

• Check VA

• Do an OCT if VA 6/12 or worse?

• Otherwise rescreen in 6 months?

Thank You

Modelled visual acuity changes for “CSMO”