the serologic diagnosis of celiac disease in adults...dr. p. vermeersch dr. g. mariën and prof. dr....

Critically Appraised Topic

The serologic diagnosis of celiacThe serologic diagnosis of celiac

Critically Appraised Topic

The serologic diagnosis of celiac The serologic diagnosis of celiac disease in adultsdisease in adults

Dr. P. VermeerschDr. G. Mariën and Prof. Dr. X. Bossuyt

Introduction

Celiac disease is an autoimmune disorder characterized by an- Celiac disease is an autoimmune disorder characterized by animmunologic responsiveness to ingested gluten

- Diagnosis is based on intestinal biopsy (Marsh classification)

G ti tibilit (HLA DQ2 d DQ8)- Genetic susceptibility (HLA DQ2 and DQ8)

- Prevalence in the general population estimated at 0.5-1%Prevalence in the general population estimated at 0.5 1%

- Most patients are diagnosed as adults and rarely present with overtceliac disease

Clinical Presentation

Hopper, A. D et al. BMJ 2007;335:558-562

Pathogenesis

Lumen Partially digested gluten peptides

Epithelial barrier Increased permeability of mucosa

Subepithelial region Gln GlutTG DQ2 / DQ8tTGAntibodies to

- Gliadin- Deamidated gliadin

tTG

APC

DQ2 / DQ8

T cellIFN-γ

B cell

- tTG- Neo-epitope

T-cellB-cell

Marsh Classification

Marsh 1 Marsh 2Intra-epithelial CryptMarsh 1 Marsh 2Intra-epitheliallymphocytosis

Crypthyperplasia

Marsh 3b Marsh3cSubtotal villous atrophy Total villous atrophy

Serology- Serologic testing is traditionally performed as a screening assay in

patients suspected of celiac disease

- Current methods include the detection of antibodies direct against:1. Endomysium (indirect immunofluorescence)2. Tissue transglutaminase (ELISA)3. Gliadin (ELISA)

- Detection of IgA antibodies is considered the most sensitive and

specific

- IgA anti-endomysial antibodies and IgA anti-tTG antibodies areIgA anti endomysial antibodies and IgA anti tTG antibodies are

considered the best screening assay in adults (sens. and spec. >90%).

Meta-analysis (2005, Rostom et al)

Studies in adults N Sensitivity (95%

CI)Specificity (95%

CI) Prev PPV NPVadults CI) CI)IgA-AGA 11 0.75–0.90 (H) 0.80–0.90 (H) 0.36 H H

IgG-AGA 7 0.17-1.00 (H) 0.70-0.80 (H) 0.37 H H

IgA-EMA (ME) 11 0.974 (0.957-0.985) 0.996 (0.988-0.999) 0.40 0.974 0.996

IgA-EMA (HUC) 6 0.902 (0.859-0.934) 1.000 (0.991-1.000) 0.33 0.902 1.000g ( ) ( ) ( )

IgA-tTG (GP) 5 0.859 (0.808-0.898) 0.953 (0.930-0.969) 0.31 0.859 0.953

IgA-tTG (HR) 3 0.0.981 (0.901-0.997) 0.981 (0.958-0.991) 0.16 0.981 0.981IgA tTG (HR) 3 0.0.981 (0.901 0.997) 0.981 (0.958 0.991) 0.16 0.981 0.981

H: Heterogeneous; ME: monkey oesophagus; HUC: human umbilical cord; GP: guinea pig; HR: human recombinant

Rostom et al. Gastroenterology 2005;128:S38-S46


Studies in Adults N Sensitivity (95%

CI)Specificity (95%

CI) Prev PPV NPVAdults CI) CI)IgA-AGA 11 0.75–0.90 (H) 0.80–0.90 (H) 0.36 H H

IgG-AGA 7 0.17-1.00 (H) 0.70-0.80 (H) 0.37 H H

IgA-EMA (ME) 11 0.974 (0.957-0.985) 0.996 (0.988-0.999) 0.40 0.974 0.996

IgA-EMA (HUC) 6 0.902 (0.859-0.934) 1.000 (0.991-1.000) 0.33 0.902 1.000g ( ) ( ) ( )

IgA-tTG (GP) 5 0.859 (0.808-0.898) 0.953 (0.930-0.969) 0.31 0.859 0.953


H: Heterogenous; ME: monkey oesophagus; HUC: human umbilical cord; GP: ginea pig; HR: human recombinant

1) Performance of anti-gliadin antibodies is inferior to anti-endomysium or anti-tTG



CI)Specificity (95%


IgG-AGA 7 0.17-1.00 (H) 0.70-0.80 (H) 0.37 H H

IgA-EMA (ME) 11 0.974 (0.957-0.985) 0.996 (0.988-0.999) 0.40 0.974 0.996

IgA-EMA (HUC) 6 0.902 (0.859-0.934) 1.000 (0.991-1.000) 0.33 0.902 1.000g ( ) ( ) ( )

IgA-tTG (GP) 5 0.859 (0.808-0.898) 0.953 (0.930-0.969) 0.31 0.859 0.953




2) Sensitivity appears lower when more patients are included with low2) Sensitivity appears lower when more patients are included with low grade histologic damage



CI)Specificity (95%


IgG-AGA 7 0.17-1.00 (H) 0.70-0.80 (H) 0.37 H H

IgA-EMA (ME) 11 0.974 (0.957-0.985) 0.996 (0.988-0.999) 0.40 0.974 0.996

IgA-EMA (HUC) 6 0.902 (0.859-0.934) 1.000 (0.991-1.000) 0.33 0.902 1.000g ( ) ( ) ( )

IgA-tTG (GP) 5 0.859 (0.808-0.898) 0.953 (0.930-0.969) 0.31 0.859 0.953




2) Sensitivity appears lower when more patients are included with low2) Sensitivity appears lower when more patients are included with low grade histologic damage

3) PPV is likely lower when applied to a low prevalence population

IgA deficiency

- Selective IgA deficiency: primary immunodeficiency characterized by

a selective deficiency of IgA in patients with normal serum levels of

IgG and IgM in whom other causes of hypogammaglobulinemia have

been excluded.

- The frequency in Western Europe is estimated at 1/400-1/900.

- When IgA antibodies are determined it is important to rule out- When IgA antibodies are determined, it is important to rule out

selective IgA deficiency since CD occurs 10-15 times more often in

these patients than in the general populationthese patients than in the general population.

=> Determine serum IgA in all patients who have a IgA anti-tTG

Current Algorythm

Request IgA anti-tTG

Serum IgAg

Normal or increased(Adults ≥0.82 g/L)

Decreased(Adults <0.82 g/L)

IgA anti-tTGIgG anti-Gliadin

130 ti t 2050 ti t130 patients 2050 patients

Critical Appraisal

- Questions have been raised regarding the diagnostic performance of

IgA anti-tTG testing in routine clinical practice.

Th t d hi h iti iti d ifi iti i ht b l t d t- The reported high sensitivities and specificities might be related to

the use of pre-selected groups of celiac disease patients (e.g. severe

histological changes of the small bowel) and/or controls.

- The specificity of the IgG anti-gliadin assay is not good- The specificity of the IgG anti-gliadin assay is not good.

- There are reports that increased serum IgA can cause false-positive

IgA anti-tTG results, but this has not systematically been studied.

Questions

1) What is the diagnostic performance of IgA anti-tTG in routine clinical

practice?p

2) Does taking into account IgA anti-tTG titer and IgA concentration

improve clinical interpretation?

3) Is the detection of IgG antibodies against deamidated gliadin3) Is the detection of IgG antibodies against deamidated gliadin

peptides (IgG DGP-AGA) a better alternative than IgG anti-gliadin

tib di (I G AGA) i ti t ith l ti I A d fi i ?antibodies (IgG AGA) in patients with a selective IgA deficiency?

Methods

- Retrospective analysis over a 42-month period to determine the

performance of IgA anti-tTG

C ti I A d fi i t ( 0 82 /L) ti t d 16- Consecutive non-IgA deficient (≥0.82 g/L) patients aged 16 years or

older who had a IgA anti-tTG and for whom biopsy results were

available were identified (558/2050).

- Patients who were previously diagnosed with celiac disease or- Patients who were previously diagnosed with celiac disease or

dermatitis herpetiformis, a severe skin manifestation of gluten

sensitivity associated with celiac disease or that were on a glutensensitivity associated with celiac disease, or that were on a gluten-

free diet were excluded.

MethodsDiagnosis of celiac disease by the clinician was consideredconfirmed when:- Duodenal biopsy showed Marsh 3

- Duodenal biopsy showed Marsh 1 or 2 and the patient responded to a glutenfree diet clinically or on duodenal biopsy

Ski bi i di d d i i h if i d h l i di d- Skin biopsy indicated dermatitis herpetiformis and the lesions disappearedwith a gluten free diet

Patient was diagnosed as non-celiac disease when:- Duodenal biopsy showed Marsh 0 and the clinician did not consider the

biopsy to be false-negative

Results

Celiac disease Non-celiac diseaseDemographic data

Number of patients 48 558

M l /F l 15/33 207/351Male/Female 15/33 207/351

Duodenal biopsyDuodenal biopsyMarsh 0 0 522

Marsh 1 7 35

Marsh 2 3 1#

Marsh 3 34 0

D titi h tif i 4 0Dermatitis herpetiformis 4 0

# P ti t di d ith i di i# Patient was diagnosed with giardiasis

ResultsPatient results

IgA anti-tTG CD Non CD

<7 U/mL 2 513≥7 U/mL 46 45

Total 48 558

ResultsPatient results


<7 U/mL 2 513≥7 U/mL 46 45

Total 48 558

O erall sensiti it and specificitOverall sensitivity and specificity


<7 U/mL 0.04 0.92≥7 U/mL 0.96 0.08

ResultsLikelihood ratio

IgA anti-tTG CD Non CD LR

<7 U/mL 0.04 0.92 0.04≥7 U/mL 0.96 0.08 11.9

LR Interpretation1 No clinical value

>10<0 1 Clinically important differences in pretest-posttest probability<0.12-5

0.2-0.5 Small difference, may be relevant in certain clinical settings

5-100.1-0.2 Modest, but substantial difference in pretest-posttest probability



<7 U/mL 0.04 0.92 0.04≥7 U/mL 0.96 0.08 11.9

BUT: Positive predictive value was only 50.5% with a prevalence of7.9% in patients who had a biopsy



<7 U/mL 0.04 0.92 0.04≥7 U/mL 0.96 0.08 11.9

BUT: Positive predictive value was only 50.5% with a prevalence of7.9% in patients who had a biopsy

The negative predictive value, in contrast, was 99.6%.

Summary (1)

1. Overall sensitivity (95.8%) and specificity (91.9%) of our secondgeneration IgA anti-tTG assay were good and comparable to otherstudies.

2 Given a prevalence of 7 9% in patients who had a IgA anti-tTG test2. Given a prevalence of 7.9% in patients who had a IgA anti tTG testand a biopsy, the positive predictive value (PPV) of a positive IgAanti-tTG result was only 50.5%.y

Summary (1)

1. Overall sensitivity (95.8%) and specificity (91.9%) of our secondgeneration IgA anti-tTG assay were good and comparable to otherstudies.

2 Given a prevalence of 7 9% in patients who had a IgA anti-tTG test2. Given a prevalence of 7.9% in patients who had a IgA anti tTG testand a biopsy, the positive predictive value (PPV) of a positive IgAanti-tTG result was only 50.5%.y

Of note: Since only patients with biopsy results were included, specificityis most likely underestimated and the PPV overestimated dueto a selection bias.

Selection Bias

- Clinicians are more likely to propose an intestinal biopsy in patientswith a high likelihood of celiac disease or who test false-positive.

- When IgA anti-tTG+ patients who were clinically diagnosed as non-CD and IgA anti-tTG- patients who did not require a biopsy wereCD and IgA anti tTG patients who did not require a biopsy wereincluded as true negative:

prevalence decreases from 7 9% to 2 3%- prevalence decreases from 7.9% to 2.3%- PPV decreases from 50.5% to 40.9%- Specificity increases from 91 9% to 97 8%Specificity increases from 91.9% to 97.8%

Questions


practice?p






Results

IgA anti-tTG

80

100

60

80

40

20

CD + DH no CD0

CD Non CD

IgA anti-tTG concentration


Patientswith biopsy

All patients


Marsh 1 Marsh 2 Marsh 3Patients

with biopsy


IgA patients LH+ CD LH+ non CD LR

0.82-2.00 g/L 247 0.929 0.034 27.32.00-4.53 g/L 325 0.960 0.097 9.9

>4.53 g/L 34 1.000 0.32 3.1

- IgA anti-tTG only modestly increases pretest-posttest probability in patientswith an increased IgA concentrationwith an increased IgA concentration

- Increased IgA is associated with significantly higher percentage of false-

iti lt (32% 6 9%)positive results (32% vs. 6.9%)

- BUT: prevalence of celiac disease was also higher in patients with an

increased IgA concentration (26% versus 6.8%)

Likelihood ratiosLikelihood ratio

Summary (2)

Taking into account IgA anti-tTG concentration and serum IgAconcentration improves clinical interpretation.

Questions


practice?p






IgG anti-deamidated gliadin

alen

ce

od itivi

ty

ifici

ty

Prev

a

Test

Met

ho

Sens

i

Spec

i

Volta et al., 2008,Selected CD (M3) and diseasedcontrol patients

NA IgA anti-tTGIgA DGP-AGA

IgG AGAIgG DGP-AGA

EurospitalInova

EurospitalInova

96.8%83.6%73.4%84.4%

91.0%90.3%76.9%98.5%

Villalta et al., 2007Consecutive patients with completeIgA deficiency and 113 controls

NA IgG anti-tTGIgG AGA

IgG DGP-AGA

InovaRadimInova

95%40%80%

99%87%98%

Ni l i t l 2007Niveloni et al., 2007Unselected consecutive patientsattending small bowel clinic

43% IgA anti-tTGIgA DGP-AGAIgG DGP-AGA

InovaInovaInova

95.0%98.3%96.7%

97.5%93.8%100%

Ankelo et al 2007Ankelo et al., 2007Selected CD patients and healthycontrols


IgG AGAIgG DGP-AGA

BiofileIn-house

BiofileIn-house

90%92%78%75%

90%90%64%98%IgG DGP AGA In house 75% 98%


alen

ce

od itivi

ty

ifici

ty

Prev

a

Test

Met

ho

Sens

i

Spec

i



IgG AGAIgG DGP-AGA

EurospitalInova

EurospitalInova

96.8%83.6%73.4%84.4%

91.0%90.3%76.9%98.5%



IgG DGP-AGA

InovaRadimInova

95%40%80%

99%87%98%



InovaInovaInova

95.0%98.3%96.7%

97.5%93.8%100%



IgG AGAIgG DGP-AGA

BiofileIn-house

BiofileIn-house

90%92%78%75%

90%90%64%98%

=> Detection of IgG DGP-AGA is both more sensitive and more specific than detection of IgG AGA

IgG DGP AGA In house 75% 98%


alen

ce

od itivi

ty

ifici

ty

Prev

a

Test

Met

ho

Sens

i

Spec

i



IgG AGAIgG DGP-AGA

EurospitalInova

EurospitalInova

96.8%83.6%73.4%84.4%

91.0%90.3%76.9%98.5%



IgG DGP-AGA

InovaRadimInova

95%40%80%

99%87%98%



InovaInovaInova

95.0%98.3%96.7%

97.5%93.8%100%



IgG AGAIgG DGP-AGA

BiofileIn-house

BiofileIn-house

90%92%78%75%

90%90%64%98%

=> The sensitivity and specificity of IgG DGP-AGA was not superior to the much better characterized IgA anti-tTG

IgG DGP AGA In house 75% 98%

Summary (3)

1. IgG DGP-AGA appears to be a better alternative than IgG AGA inpatients with selective IgA deficiency, but cannot replace IgA anti-tTG as routine screening assay in non-IgA deficient patients.

2 Further research is needed to determine the diagnostic2. Further research is needed to determine the diagnosticperformance, especially the false-positive rate, of IgG DGP-AGA inroutine clinical practice.p

To Do’s

1. Inform clinicians that the performance of the current IgA anti-tTGassay is good.

2. To report the likelihood ratio of the relevant interval to clinicians(including confidence intervals)(including confidence intervals).

3. Evaluate the 2 currently available IgG DGP-AGA assays (Inova andEuroimmune) on the consecutive non-IgA deficient patients.

4 Replace IgG AGA with IgG DGP AGA in patients with selective IgA4. Replace IgG AGA with IgG DGP-AGA in patients with selective IgAdeficiency. The cost of both assays is comparable.

Acknowledgements

Dep. of Laboratory Medicine (UZ Leuven)p y ( )Prof. Dr. X. BossuytDr. G. MariënApr. D. Coenen

Dep of Gastroenterology (UZ Leuven)Dep. of Gastroenterology (UZ Leuven)Prof. Dr. M. Hiele

Dep. of Pathology (UZ Leuven)Prof. Dr. K. Geboes

the serologic diagnosis of celiac disease in adults...dr. p. vermeersch dr. g. mariën and prof. dr....

Documents