Commissie voor Klinische BiologieCommission de Biologie Clinique

EXTERNAL EVALUATION PROGRAM FORImmmunoassays - Chemistry

TRENDS IN TIME

CM Van Campenhout – N Hamers – JC Libeer WIV/ISP/IPH – Clinical Biology

Brussels - BELGIUM

• EQA PROGRAMS - STATISTICAL EVALUATION

• GENERAL CHANGES

• EVOLUTIONS IN IMMUNOASSAYS

• EVOLUTIONS IN CHEMISTRY

• EQA PROGRAMS – THE PLAYERS

• CONCLUSION

EQA PROGRAMS

• CLINICAL CHEMISTRY - ELECTROPHORESIS

• IMMUNOASSAYS

• HEMATOLOGY

• COAGULATION

• IMMUNOHEMATOLOGY

• FLOW CYTOMETRY

• NON INFECTIOUS SEROLOGY

• PCR / ONCO-HEMATO / MICROBIOLOGY

• HEAVY METALS

• ALLERGY

• SPERM

• HbA1c

• ALCOHOL

• POCT GLUCOSE

• MICROBIOLOGY

• PARASITOLOGY

• INFECTIOUS SEROLOGY

• THERAPEUTIC MONITORING

TYPES OF CONTROL MATERIAL

• COMMERCIAL LYOPHYLIZED (human)

• COMMERCIAL LIQUID (human)

• PATIENT SAMPLES - pools- single donation

• MICRO-ORGANISMS

• RELATIVE IMPRECISIONRELATIVE IMPRECISION (own peer group) CRITERIA

M - RZ-SCORE = --------- limit = 3Z (3SD)

SD

• RELATIVE ACCURACYRELATIVE ACCURACY (own peer group)

M - RU-SCORE = --------- x 100 limit = “d” (%)

M Based on biological variability

STATISTICAL non parametricANALYSIS OF QUANTITATIVE RESULTS

SD = P75 – P25 / 1,349

NUMBER OF RESULTS EXCEEDING THE LIMITS FOR IMPRECISION AND ACCURACY ARE ADDED

IMPRECISION (relative) ACCURACY (relative)

Z > 3SD (own peer group) U > d (fixed limit)method dependent non method dependent

LABORATORY EVALUATION FORQUANTITATIVE RESULTS

- ANNUAL REPORT-

NZ NuPercentages of Nz (=Pz) and Nu (Pu) for each laboratory are calculated

PRECISION (relative) ACCURACY (relative)

(%) 100N

NP ZZ ×⎟

⎠⎞

⎜⎝⎛= (%) 100

NNP U

U ×⎟⎠⎞

⎜⎝⎛=

90th percentile (P90) of the distribution of all Pz and all Pu values of all laboratories is calculated criterion for performance evaluation.

Pz > P(90) z Poor performance for PRECISION

Pu > P(90)u Poor performance for ACCURACY

LABORATORY EVALUATION FORQUANTITATIVE RESULTS

- ANNUAL REPORT-

Cumulative Pz- en Pu-distribution for alllaboratories - EQA CHEMISTRY 2009 - (N=213)

0

20

40

60

80

100

120

0 5 10 15 20 25 30 35Percentage z-scores and u-scores "out of limit values"

Cum

ulat

ive

freq

dis

trib

.o

Pz

Pu

• EQA PROGRAMS - STATISTICAL EVALUATION

• GENERAL CHANGES

• EVOLUTIONS IN IMMUNOASSAYS

• EVOLUTIONS IN CHEMISTRY

• EQA PROGRAMS – THE PLAYERS

• CONCLUSION

CHANGES OVER TIME - GENERAL

• CHANGES IN NUMBER OF PARTICIPATING LABORATORIES

• CHANGES IN REQUESTED ANALYTES

• MAJOR CHANGES IN METHODOLOGIES

• MAJOR CHANGES IN REPORTING EQA RESULTS

050

100150200250300350400450

BIOCHEMISTRY IMMUNOASSAY

19952008

EVOLUTION OF PARTICIPATING LABORATORIES

• INCREASE IN REQUESTED ANALYTES

• CHANGES IN METHODOLOGY

EVOLUTION IN EQA IMMUNOASSAYS

VancomycinValproic acidTheophyllinePhenytoinPhenobarbitalParacetamolLithiumGentamicinDigoxinCarbamazepinAmikacinSalicylate

Anti TG/TPOVitamin B12TSHThyroglobulinTestosteronPSAProlactineProgesteroneParathormoneOestradiolNSELHInsulinIgE

hGHhCGFT4FT3FSHFolateFerritineDHEA-Sc-PeptideCortisolCEACA 19.9CA 15.3CA 125AFP

REQUESTED ANALYTES EQA IMMUNASSAYS

1995

VancomycinValproic acidTheophyllinePhenytoinPhenobarbitalParacetamolLithiumGentamicinDigoxinCarbamazepinAmikacinSalicylate

Anti TG/TPOVitamin B12TSHThyroglobulinTestosteronPSAProlactineProgesteroneParathormoneOestradiolNSELHInsulinIgE

hGHhCGFT4FT3FSHFolateFerritineDHEA-Sc-PeptideCortisolCEACA 19.9CA 15.3CA 125AFP

REQUESTED ANALYTES EQA IMMUNASSAYS

1995 - 2008

0.0

20.0

40.0

60.0

80.0

100.0

%RIA % non RIA

EXAMPLE FOR PROGESTERON

1996 1997 1998 1999 2000 2001 2002 2003

CHANGES IN METHODOLOGY

from RIA to non RIA METHODS

0102030405060708090

RIA non RIA

20%28%

CV(%) IN FUNCTION OF TIME

RIA and non RIA METHODS

CV(%)

1996 1997 1998 1999

EXAMPLE FOR PROGESTERON

0

5

10

15

20

25

30

35

40

Immunotech(4)

Siemens(coat-a-

count) (9)

Access (6)

Liaison (6)

Elecsys Cobas e

(29)

Immulite (38)

Global (102)

Patient 1.68 µmol/LBiorad 1.69 µmol/LPatient 1.69 µmol/LBiorad 14.20 µmol/LRandox 25.00 µmol/L

DHEA-S CV (%)

CV(%) IN FUNCTION OF METHODS

Analytical systems

(n=4) Coat-a-count(n=9) (n=6)

(n=29)(n=38) (n=102)(n=6)

05

101520253035404550

AFP*

CEA

*

Cortisol

Ferritine

FSH

FT3*

FT4*

hCG

IgE

LH Progesteron

Prolactine*

PSA

Testosteron*

TSH

Vit B12

d (%)1993/2004*d (%) 2008TE-WESTGARD

EVOLUTION OF FIXED LIMITS “d” IN TIME

0

5

10

15

20

25

30

Am

ikacine*

Digoxine

Theophylline

Valproïnezuur*

Vancom

ycine* d (%)1993/2004*d (%) 2005 d (%) 2008

EVOLUTION OF FIXED LIMITS “d” IN TIME

1994 1996 1998 2000 2002 2004 2006 2008

14

12

10

8

6

4

CYCLE

P(90

) Z

1994 1996 1998 2000 2002 2004 2006 2008

18

16

14

12

10

8

6

4

CYCLE

P(90

) U

INTRODUCTION OF NEW

PARAMETERS

CHANGES IN CONCENTRATIONS

(e.g. low values)

EVOLUTION OF

PU and Pz IN TIME

P(90)U

P(90)Z

• INCREASE IN REQUESTED ANALYTES

• CHANGES IN METHODOLOGY

EVOLUTION IN EQA CHEMISTRY

eGFR*γ GTCREATININECHOLESTEROL TOTALCHOLESTEROL – HDL*CHLORIDESCALCIUMBILIRUBINE TOTAL*BILIRUBINE DIRECTE*AST*AMYALSEALTALBUMIN*

REQUESTED ANALYTES EQA CHEMISTRY

1995

GLUCOSEIgAIgGIRONLDHMAGNESIUMPHOSPHORUS*POTASSIUMSODIUMTOTAL PROTEINTRIGLYCERIDESURIC ACIDUREA

eGFR*γ GTCREATININECHOLESTEROL TOTALCHOLESTEROL – HDL*CHLORIDESCALCIUMBILIRUBIN TOTAL*BILIRUBIN DIRECT*AST*AMYLASEALTALBUMIN*

REQUESTED ANALYTES EQA CHEMISTRY

1995 - 2008

GLUCOSEIgAIgGIRONLDHMAGNESIUMPHOSPHORUS*POTASSIUMSODIUMTOTAL PROTEINTRIGLYCERIDESURIC ACIDUREA

CHANGES IN METHODOLOGIES

• UNIFORMIZATION OF TEMPERATURE FOR ENZYMES

• ELECTROLYTES: Flame photometry POTENTIOMETRY

• STANDARIZATION OF SERUM PROTEINS (CRM 470)

• STANDARDIZATION OF CREATININE (IDMS)

ELECTROLYTES

• SODIUM

• POTASSIUM

• CHLORIDES

• CALCIUM

POTASSIUM (mmol/L)

NCV(%)MEDIANSURVEY

3681.72.0

4.906.41

1994/04

3791.83.0

6.427.39

1994/03

3932.92.6

3.805.80

1994/02

3842.92.2

5.207.00

1994/01

NCV(%)MEDIANSURVEY

2102.20.9

6.284.00

2009/01

2041.71.3

4.805.10

2008/03

2072.21.4

3.306.22

2008/02

2101.51.2

4.006.26

2008/01

CHLORIDES (mmol/L)

NCV(%)MEDIANSURVEY

2083.22.3

116.098.7

2009/01

2074.31.9

86.0116.8

2008/02

2103.22.8

116.099.0

2008/01

2111.92.9

116.0103.0

2007/03

NCV(%)MEDIANSURVEY

3592.84.0

107.0111.0

1994/04

3674.06.0

111.0126.0

1994/03

3825.14.4

102.085.0

1994/02

3736.34.2

70.588.0

1994/01

SODIUM (mmol/L)

NCV(%)MEDIANSURVEY

2092.11.5

142.0144.6

2009/01

2041.71.5

151.0150.0

2008/03

2061.81.9

122.0160.0

2008/02

2092.11.5

141.8145.0

2008/01

NCV(%)MEDIANSURVEY

3681.82.7

145.0138.0

1994/04

3792.71.3

138.0171.0

1994/03

3931.61.7

136.0111.0

1994/02

3842.91.6

107.2121.0

1994/01

CALCIUM (mmol/L)

NCV(%)MEDIANSURVEY

2092.62.4

3.152.35

2008/04(Serum)

2042.63.2

2.352.35

2008/03

2073.32.6

2.083.15

2008/02

2092.92.9

3.182.38

2008/01

NCV(%)MEDIANSURVEY

3833.53.6

3.292.45

1994/04

3913.84.1

3.303.05

1994/03

4114.63.5

2.082.93

1994/02

3983.53.3

3.222.50

1994/01

0,00

1,00

2,00

3,00

4,00

5,00

6,00

1999

1999

2000

2000

2001

2001

2002

2002

2003

2003

2004

2004

2005

2005

2006

2006

2007

2007

2008

2008

Arsenazo O-Cresol Indirect Pot.

EVOLUTION OF CV(%) for CALCIUM OVER TIME

CHANGES IN METHODOLOGIES

• UNIFORMIZATION OF TEMPERATURE FOR ENZYMES

• ELECTOLYTES: Flame photometry POTENTIOMETRY

• STANDARIZATION OF SERUM PROTEINS (CRM 470) - 1994

• STANDARDIZATION OF CREATININE (IDMS)

IgG (g/L)

NCV(%)MEDIANSURVEY

1656.66.4

7.816.21

2008/02

1667.26.8

6.805.90

2007/04

1645.14.9

7.317.32

2007/02

1646.46.2

11.757.86

2007/01

NCV(%)MEDIANSURVEY

34415.816.0

7.8711.30

1993/04

35318.217.6

10.208.39

1993/03

35214.817.4

9.327.53

1992/04

35415.518.2

5.9412.28

1992/01

BEFORE BEFORE CRM 470 AFTERAFTER CRM 470

IgA (g/L)

NCV(%)MEDIANSURVEY

1658.67.9

1.551.32

2008/02

1667.47.7

1.461.34

2007/04

1647.87.3

1.521.52

2007/02

1666.47.8

2.901.62

2007/01 35417.823.2

1.292.47

1992/01

NCV(%)MEDIANSURVEY

34218.319.0

1.702.50

1993/04

35223.819.9

2.221.90

1993/03

36220.319.3

1.892.08

1992/03

BEFOREBEFORE CRM 470 AFTERAFTER CRM 470

0,00

5,00

10,00

15,00

20,00

25,00

30,00

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

EVOLUTION of CV(%) over time

Introduction of CRM 470CRM 470

CRM 470

IgA

0,00

5,00

10,00

15,00

20,00

25,00

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

CRM 470

IgG

CREATININE(µmol/L)

NCV(%)MEDIANSURVEY

2105.15.3

128.0347.0

2009/01

2048.27.1

72.273.2

2008/03

2079.74.2

102.0362.0

2008/02

2095.14.7

128.0347.0

2008/01

NCV(%)MEDIANSURVEY

4175.85.6

167.0344.0

1994/04

4236.25.7

344.0189.0

1994/03

44618.77.0

115.0597.0

1994/02

4345.66.3

212.0307.0

1994/01

EVOLUTION OF FIXED LIMITS “d” IN TIME

0

5

10

15

20

25

30

35

40

45

50

Album

in*

ALA

T

Am

ylase

ASA

T*

Bilirubin direct*

Bilirubin total*

Calcium

Cholesterol

Chloride

Creatinine

Phosphorus*

g GG

T

Glucose

HD

L-Cholesterol *

IgA

IgG

Iron

Potassium

LDH

Magnesium

Sodium

Protein total

Triglycerides

Urea

Uric A

cid

d (%) 1993/2004*d (%) 2008TE - WESTGARD

1992 1994 1996 1998 2000 2002 2004 2006 2008

35

30

25

20

15

10

5

P(90

) U

1992 1994 1996 1998 2000 2002 2004 2006 2008

18

16

14

12

10

8

6

4

P(90

) Z

EVOLUTION OF

PU and Pz IN TIME

P(90)U

P(90)Z

• 2006 - Changes in fixed limit “d”• Amylase• K• Mg• Cholesterol tot/HDL• Glucose• LDH• Uric acid• Iron• Urea

5,43,922,22020gGT

1,51,210,210,210,2Phosporus*

2,99,38,28,38,3Creatinine

2,617,41,533Chlorides

2,41,68,5910,5Cholesterol tot..

1,58,92,44,54,5Ca

3,410,931,116,216,2Bilirubin tot.*

8,39,644,524,124,1Bilirubin dir.*

2,64,515,215,215,2AST*

2,51,614,61517Amylase

2,812,632,12020ALT

4,215,73,96,26,2Albumin*

Z > 3%

U > d%

TE -WESTGARD

d (%) 2008

d(%) 1993 2004*

ANALYTE

4,21,512,411,915Uric acid

1,50,615,715,721Ureum

5,80,227,92020Triglyc.

2,14,83,45,55,5Proteins tot.

2,414,20,922Na

3,12,54,88,89,5Mg

3,71,011,411,414LDH

6,91,45,85,88K

2,32,230,79,520Ijzer

2,94,0811,511,5IgG

4,21,013,51919IgA

3,04,411,113,415HDL-Chol.*

1,91,56,96,914Glucose

Z >3%

U > d%

TE -WESTGARD

d (%) 2008

d(%)1993

2004*ANALYTE

FIXED LIMITS (d) - TEa - U > d (%) - Z > 3 (%)

FIXED LIMITS ARE BASED ON Westgard TEa or on the 90th percentile of intra-laboratory CV’s (multiplied by 3) of about 10 laboratories using different techniques

CHANGES OVER TIME - GENERAL

DECREASE IN NUMBER OF PARTICIPATING LABORATORIES

INCREASE IN REQUESTED ANALYTES

MAJOR CHANGES IN METHODOLOGIES

MAJOR CHANGES IN REPORTING EQA RESULTS

CHANGES OVER TIME - GENERAL

AMELIORATION OF RELATIVE ACCURACY

AMELIORATION OF RELATIVE PRECISION

MAJOR CHANGES IN METHODOLOGIES dedicated systems generally lesser method principles (ex enzymes, electrolytes,…)

MAJOR CHANGES IN REPORTING EQA RESULTS more documented reports – educative messages – graphs - …….

EQA PROGRAMS - THE PLAYERS

PARTICIPANTS = LABORATORIES

ORGANIZERS = WIV/ISP

EQUIPEMENT/REAGENTS = MANUFACTURERS

ALL PLAYERS AFFECT THE RESULTS OF EQA SURVEYS

LABORATORIES

MANUFACTURERS

EQA ORGANIZERSWIV/ISP

INCORRECT choice of units (e.g. mg/dL – mmol/L)

INCORRECT choice of method

INCORRECT interpretation of “limit of detection” and limit of quantification (LOQ ≠ LOD)

INCORRECT SAMPLE IDENTIFICATION

PARTICIPANTS - LABORATORIES

ORGANIZERS = WIV/ISP

CHOICE OF CONTROL MATERIAL

CONCENTRATION RANGES

FIXATION OF LIMIT “d”

PARTITION OF METHODS AND METHOD GROUPSMEASURING PRINCIPLEMANUFACTURER

2084.40 3.4%0.05 1.42 Global results (all methods and all measuring systems)

64.43 1.70.02 1.43 310 Unreduced phosphomolyb./ UV-Siemens (Bayer)

574.41 1.70.02 1.42 309 Unreduced phosphomolyb./ UV-Roche (Hit/Modular)

594.30 3.40.05 1.39 308 Unreduced phosphomolyb./ UV-Roche (Cobas/Integra)

124.40 3.00.04 1.42 307 Unreduced phosphomolyb./ UV-Olympus

64.27 3.50.05 1.38 306 Unreduced phosphomolyb./ UV-Siemens (Dade)

164.83 3.10.05 1.56 305 Unreduced phosphomolyb./ UV-Coulter (Beckman)

154.30 2.60.04 1.39 304 Unreduced phosphomolyb./ UV-Abbott

354.50 3.20.05 1.45 303 Reflectometry - OCD

2********1.48 - 1.54 301 Unreduced phosphomolyb./ UV-Other

N labsMedianmg/dL

CV%

SDmmol/L

Medianmmol/L METHOD

C/8202 (2009/01)PHOSPHORUS - d (%) : 10.2

C/8181 (2008/01)PHOSPHORUS - d (%) : 10.2

4.41

4.41

4.41

Medianmg/dL

2093.4%0.051.42Global results (all methods and all measuring systems)

351.7%0.021.42003 Reflectometry - OCD

2********1.41-1.45002 Reduced phosphomolybdate complex / VIS

1723.4%0.051.42001 Unreduced phosphomolybdate complex / UV

No.labsCV%SDMedian

Mmol/LMETHOD

C/8181 METHOD 11,65

1,55

1,45

1,35

1,25

MANUFACTURER

PH

OS

PH

OR

US

(m

mol

/L)

1 2 3 4 5 6 7

PHOSPHORUS – 2008/01

C/81818/19 labs U > d (=10,5%) 12/19 labs R > 3Z

001 Unreduced phosphomolybdate complex / UV

310 Unreduced phosphomolyb./ UV-Siemens (Bayer)

309 Unreduced phosphomolyb./ UV-Roche (Hit/Modular)

308 Unreduced phosphomolyb./ UV-Roche (Cobas/Integra)

307 Unreduced phosphomolyb./ UV-Olympus

306 Unreduced phosphomolyb./ UV-Siemens (Dade)

305 Unreduced phosphomolyb./ UV-Coulter (Beckman)

304 Unreduced phosphomolyb./ UV-Abbott

303 Reflectometry - OCD

301 Unreduced phosphomolyb./ UV-Other

413416N

2,664,33P Z (%)

1,456,40P U (%)

2009/012008/01

INFLUENCE OF PEER GROUPING ON p U(%)

% citations for U > d; relative accuracy

0%

2%

4%

6%

8%

10%

12%

14%

16%

18%

20%

ALBUMIN ALT

AMYLA

SE AST

BILIRUB

IN TOTA

L CA

LCIUM

CH

LORIDE

CHOLEST

EROL-HDL

CHOLEST

EROL-Tota

lCREA

TININE

GGT

GLUCOSE

IGA

IGG

IRON

LDH

MAGNES

IUM

PHOSPHORUS POTA

SSIUM

SODIUM

TOTA

L PROTE

IN

TRIG

LYCERID

ES UR

ATE

UREA

p U% 2008/1p U% 2009/1

INFLUENCE OF PEER GROUPING ON p Z(%)

0%

1%

2%

3%

4%

5%

6%

7%

8%

ALBUMINALT

AMYL

ASE

AST

BILIRUBIN TO

TAL

CALCIUM

CHLORIDE

CHOLEST

EROL-H

DL

CHOLEST

EROL-T

otal

CREATIN

INEGGT

GLUCOSE IGA

IGG IRON LD

H MAGNES

IUMPH

OSPHORUS

POTA

SSIUM

SODIUM

TOTA

L PROTE

IN

TRIGLY

CERIDESURATE

UREA

p Z% 2008/1p Z% 2009/1

% citations for Z > 3; relative imprecision

EQUIPEMENT/REAGENTS = MANUFACTURERS

INFORMATION ON NEW or CHANGED REAGENT / EQUIPEMENT

MEASURING PRINCIPLECALIBRATION

INFORMATION ON CALIBRATION / LINEARITY

CORRECT AND FULLY DOCUMENTED INSERTS

COMMUNICATION WITH WIV/ISP ON EPXIRED REAGENTS/EQUIPEMENT

BILIRUBIN TOTAL (21670) µmol/l C/7521 METHOD Median SD CV No.labs

1 Diazo sulfanilic acid 85.50 5.45 6.4% 97 2 Diazo sulfanilic acid (blue color) 83.79 2.09 2.5% 19 4 Dichloraniline 89.18 4.82 5.4% 6 5 Diphenyldiazonium (DPD) 84.47 3.80 4.5% 42 6 Reflectometry 75.41 3.11 4.1% 35 7 Reduction (biliverdin) 78.15 3.04 3.9% 9 obal results (all methods and all measuring systems) 83.70 5.39 6.4% 208

B IL IR U B IN T O T A L - d (% ) : 1 6 .2 C o n ve rs io n fa c to r : µ m o l/L / 1 7 .1 = m g /d L C /7 5 22

M E T H O D M e d ia nµ m o l/L

S D µ m o l/L

C V %

M e d ia nm g /d L N lab s

3 01 D ia zo su lfa n ilic a c id -S ie m e n s (D a d e ) 7 6 .9 5 0 .2 5 0 .3 4 .5 0 6 3 02 D ia zo su lfa n ilic a c id (b lue co lo r)-C o u lte r 8 3 .1 1 1 .8 4 2 .2 4 .8 6 16 3 03 D ia zo su lfa n ilic a c id -O the r 8 7 .2 1 - 8 5 .1 5 2 3 04 D ich lo ra n iline - A bbo tt 7 0 .1 1 5 .0 7 7 .2 4 .1 0 13 3 05 D ip h en y ld ia zo n iu m (D P D )-O lym pu s 8 5 .8 4 1 .8 7 2 .2 5 .0 2 12 3 06 R e fle c to m etry-O C D 7 3 .1 9 3 .7 4 5 .1 4 .2 8 35 3 07 R ed u ction (b ilive rd in )-S ie m e n s (B a ye r) 7 7 .8 9 2 .6 6 3 .4 4 .5 5 6 3 09 R ed u ction (b ilive rd in )-A b b o tt 7 4 .5 6 - 7 7 .6 3 2 3 10 D ia zo su lfa n ilic a c id -R o ch e (C o b as/In teg ra ) 7 9 .1 7 7 .6 1 9 .6 4 .6 3 17 3 11 D ia zo su lfa n ilic a c id -R o ch e (H it/M o du la r) 7 3 .8 7 6 .6 5 9 .0 4 .3 2 55 3 12 D ip h en y ld ia zo n iu m (D P D )-R o ch e (C o b a s) 7 5 .5 0 6 .9 7 9 .2 4 .4 1 42 G lo b a l re s u lts (a ll m e th o d s an d a ll m e a s u rin g s ys te m s ) 7 5 .6 7 7 .1 0 9 .4 4 .4 2 2 0 6

?

EQA is not just statistics !

LABORATORIES

MANUFACTURERS

EQA ORGANIZERSWIV/ISP

evaluation - amelioration - education – communication Having confidence is good, to check your confidence is better…

Coming up soon – 2009 / 2010

•DOA – urine

•Cardiac markers

•Specific proteins

•CRP

With sincere thanks to all laboratories for their willing collaborationN Hamers – Y Lenga – C Van Campenhout – P Van de Walle