Blood Gas Reference Intervals

The Struggle Continues

Roger Ashton

Pathlab Whakatane

Walking on eggshells

Riding on the shoulders of those who have tried before

Lynne Clarke – Waikato

Tony Mace - Pathlab

And many others including :

RCPA

ARQAG

AACB

Blood Gas Reference

Intervals

Lyn Clarke

Dip MLT, BBS

June2016

Analysers in New Zealand

Radiometer – majority of large volume sites

41 ABL800

11 ABL80

25 ABL90

iSTAT – Large numbers in low volume sites

Siemens – A few sites APPROX 9

GEM At least 2

? Others e.g. Epoch, Roche, Novastat

12 New Zealand Locations

Reality

Few Laboratories have references in their methods. • Some use vendor ranges.

There is a lot of data on cord bloods

Plenty of data on animals

Very little data on adults

Text books often have no references or reference each other e.g Tietz, Sigaard-Andersen, Wallach, New England Medical Journal

Still cannot get agreement on UNITS

Klaestrup et al 2011

182 patients

Medical Students and health professionals

118 medical students practising on each other

76% <40 yrs (138)

Age range 20-76 yrs

Radiometer analyser

Conclusions 2015

CLSI now allows for Consensus Ranges

Logically the ranges should be the same throughout the

country.

Get buy in from Pathologists

Set up a meeting of the participants

iSTAT

Comparison of Reference Intervals REFERENCE RANGES LITERATURE

Test Age Range

Tietz 4th ed

2006

ABBOTT

ISTAT Radiometer

Klaestrup et

al (2011)

Widdop

(2002)

Cousineau et al

( 2006) Helwig (1996) Yeomans (1985) Victory (2004) Shirley (1996)

Number in study ? ? ? 182 126 16060 146 20456 53 pH Arterial 1 Day 7.29-7.45 7.35 - 7.45 7.35-7.45

Male 7.376 -7.455

Female 7.35-7.45 7.384-7.468

Female/Male 7.35 - 7.45 7.382 - 7.462

pH Venous Adult 7.32-7.43 7.31 - 7.41

60-90 7.31-7.42

pH - Capillary 36-60 hours 7.312-7.473

pH Cord Blood- Arterial 7.28±0.05 7.10-7.38 7.15-7.43 7.17-7.31

pH Cord Blood - Venous 7.35±0.05 7.20-7.46 7.24-7.49 7.27-7.45

pO2 Arterial 1 Day

54-95 mmHg

7.18-12.64 kPa

>1 Day

83-108 mmHg

11.04-14.36 kPa

83-108 mmHg

11.07-14.4 kPa 11.1-15.5 kPa

pO2 Venous

pO2 Capillary 36-60 hours 32.8- 61.2 mmHg

pO2 Cord Blood- Arterial

80 -105 mmHg

6.7 -14 kPa 6-30 mmHg 3.8-33.8 mmHg

pO2 Cord Blood - Venous 16-43 mmHg 15.4-48.2 mmHg

pCO2 Arterial Newborn

27-40 mmHg

3.59-5.32 kPa

Adult Male

35-48 mmHg

4.66-6.38 kPa

35-45 mmHg

4.67 - 6.0 kPa

35-48

mmHG(M/F)

4.67-6.40 kPa 4.5-6.0 kPa

Adult Female

32-45 mmHg

4.26 - 5.99 kPa

35-45 mmHg

4.67 - 6.0 kPa 4.1 - 5.6 kPa

Female/Male 4.3-6.0 kPa

pCO2 Venous

0.8-0.83 kPa

Higher than

arterial

41-51 mmHg

5.47 - 6.8 kPa

Where we are currently

pH

Tietz (2006) 7.35 – 7.45

Wallach (1996) 7.36 – 7.44

Radiometer, Siemens iSTAT 7.35 – 7.45

Klaestrup et al (2011) 7.382 – 7.462

pH

Propose 7.35 - 7.45

pO2

Adult

Semantics and conversion factors

0

20

40

60

80

100

120

140

160

0 5 10 15 20 25

mmHg

KPA mmHg

1 7.5

2 15

4 30

6 45

8 60

10 75

12 90

14 105

16 120

18 135

20 150

KPA mmHg

1 7.5

2 15

3.5 26.25

4 30

6 45

6.7 50.25

7 52.5

7.6 57

8 60

9.34 70.05

9.5 71.25

10 75

10.65 79.875

10.66 79.95

10.67 80.025

11.34 85.05

11.4 85.5

12 90

13.3 99.75

14 105

16 120

18 135

20 150 • Do we want our Reference Range to be exact?

• To how many decimals?

• Or Memorable?

• Or close enough?

• Or Clinically Significant

NUMERICAL CREEP

11 KPa = 82.5 mmHg

“ Let’s call it 83”

83 mmHg = 11.1 KPa

“must be exact”

80 ~ 10.7

85 ~ 11.4

100 ~ 13.3

108 ~ 14.4

PO2 Adult

Low 70 – 85 mmHg = 9.3 – 11.4 KPa

High 100 - 108 mmHg = 13.3 - 14.4 Kpa

9.3 - 14.4 Kpa ?? Too wide, and not referenced ??

ORIGINAL PROPOSAL

Tietz 83 - 108 mmHg = 11.0 to 14.4 KPa

P O 2

ARQAG Proposal

75 - 105 mmHg 10 - 14 KPa

PCO2

Test Age Range ADHB Christchurch Waikato Wellington WDHB Hawkes Bay Whakatane

pCO2 Arterial 4.6-6.0 kPa 24-30.0 mmHg 4.5-6.0 kPa 35-45 mmHg 4.6 -6.0 KPA 35-45 4.67 - 6.00 kPa

pCO2 Venous 5.0-6.4 kPa 25-33.0 mmhg 5.0-6.4 kpa 38-48 mmHg 41-51 5.47 - 6.8 kPa

Wider variation depending on source

Tried looking at Low & High separately

Some sources had different Male and Female

PCO2 Adult Low MALE 32 – 37 mmHg = 4.3 – 4.9 KPa

Low FEMALE 27 – 32 = 3.6 – 4.3 Kpa

LOW limit NZ LABS 24 – 30 = 3.4 – 4.0 Kpa

High MALE 45 – 48 = 6.0 – 6.66

High FEMALE 43 – 45 = 5.6 – 6.0

High limit NZ LABS 30 – 48 = 4.0 – 6.67 Kpa

DO WE NEED GENDER SPECIFIC RANGES ??

PCO2 Adult

Tietz

Male 35 – 48 mmHg = 4.7 – 6.4 KPa

Female 32 – 45 mmHg = 4.3 – 6.0 KPa

ARQAG PROPOSAL

35 - 45 mmHg 4.7 - 6.0 KPa

Consensus Recommendation

NZPOCTQAG / ARQAG

NSW Pathology • source

pH 7.35 - 7.45 Tietz

PO2 75 - 105 mmHg = 10.0 to 14.0 Kpa Tietz / ARQAG

PCO2 35 – 45 mmHg = 4.7 to 6.0 KPa Tietz / ARQAG

HCO3 22 to 28 mmol/L

Base Excess -3 to +3 mmol/L

Lactate less than 2.0 mmol/L

Cord Bloods Agreed 2018

What is next?

HAEMOGLOBIN

HaemQAG RCPA

Haematology nationwide recommendations 2014

Needed “pruning” to give 10 age related for use in POC

Number of significant figures

The reference intervals are rounded regardless of the

number of decimals in the original source.

pH: Rounded to 2 decimal places.

pCO2: Rounded to 0 decimal place for mmHg and 1 decimal place for kPa.

pO2: Rounded to 0 decimal place for mmHg and 1 decimal place for kPa.

ctHb: Rounded to 0 decimal place. (1 decimal for g/dl )

sO2: Rounded to 0 decimal place for % and 2 decimal places for fraction.

Laboratories may choose to report to a higher number of Decimals,

but Ranges should be rounded

Other parameters

(Electrolytes, Metabolites, & Co-oximetry)

Generally follow ARQAG

Do we need separate ranges?

Serum, Plasma, Whole Blood?

Potassium

Venous Ranges

To be discussed in more detail by Rita

Currently before ARQAG

Where to next?

Propose pH , PCO2, PO2 ranges to

NZPOCTQAG

ARQAG

PATHOLOGISTS

Other Quality Groups

Suggest need for haste and assertiveness.

onions

References

B.E. Statland, Clinical Decision Levels for Lab Tests (Oradell, NJ:

Medical Economic Books, 1987).

P.C. Painter, J.Y. Cope, J.L. Smith, “Reference Ranges, Table

41–20” in Tietz Textbook of Clinical Chemistry—Second Edition,

C.A. Burtis and E.R. Ashwood, eds. (Philadelphia: W.B. Saunders

Company, 1994).

CLSI Defining, Establishing and Verifying Reference Intervals in

the Clinical Laboratory – Third Edition v28 n30

Base Excess??

Standard Base Excess ?? SBE

Actual Base Excess ?? ABE

Bicarbonate

HCO3

Plasma

Standardized

K 3.5-5.2 mmol/L

Na 135-145 mmol/L

Cl 95-110 mmol/L

pH 7.30-7.40

PO2 No RR

PCO2 5.0-6.4 Kpa 40-50 mmHg

HCO3 22-28 mmol/L

Lactate < 2.0 mmol/L

Ionized Ca 1.15-1.30 mmol/L