Use of likelihood ratios improves clinical interpretation of IgA anti-tTG antibody testing for celiac disease.
BACKGROUND
We investigated whether taking into account IgA anti-tissue transglutaminase antibody concentration (IgA anti-tTG) and total IgA concentration could improve clinical interpretation of serologic testing for celiac disease (CD).


METHODS
We retrospectively identified 43 consecutive newly diagnosed CD patients and 545 consecutive disease control patients who had an IgA anti-tTG request during the 42-month study period and for whom intestinal biopsy results were available.


RESULTS
Sensitivity and specificity of the IgA anti-tTG assay from Genesis was 95.3% and 92.7%, respectively, with a likelihood ratio (LR) of 12.4. The LR for CD markedly increased with increasing IgA anti-tTG concentration (from 2.0 for results between 7 and 20 U/ml up to 319 for results >100 U/ml). The LR for CD was also higher in patients with a normal IgA concentration (0.82-4.53 g/L) compared to patients with an increased IgA concentration (15.3 vs. 3.1, respectively). These observations were confirmed with a second IgA anti-tTG assay from BioRad.


CONCLUSIONS
Sensitivity of IgA anti-tTG was good. Specificity, however, was reduced when IgA anti-tTG was weak positive or when the IgA concentration was increased. Taking into account IgA anti-tTG concentration and IgA concentration improves clinical interpretation of serologic testing for CD.
Laboratory Medicine, Immunology, University Hospital Gasthuisberg, Catholic University of Leuven, Belgium.
Pieter
P
Vermeersch
Dries
D
Coenen
Karel
K
Geboes
Godelieve
G
Mariën
Martin
M
Hiele
Xavier
X
Bossuyt
D000328:Adult; D002446:Celiac Disease / Q000175:diagnosis* / Q000276:immunology; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D007070:Immunoglobulin A / Q000276:immunology*; D016013:Likelihood Functions; D008297:Male; D012680:Sensitivity and Specificity; D011503:Transglutaminases / Q000276:immunology*
D007070:Immunoglobulin A; D011503:Transglutaminases