Positive predictive value of serological diagnostic measures in celiac disease.

BACKGROUND: Celiac disease (CD) antibodies, immunoglobulin A (IgA) anti-tissue transglutaminase (anti-tTG), IgA endomysium antibody (EMA), IgA and IgG anti-gliadin antibodies (IgA and IgG AGA) are first-line diagnostic tools used in selecting patients for duodenal biopsy. The goal of this study was to evaluate the diagnostic quality of serological testing for CD.
METHODS: CD serological tests (IgA and IgG AGA, anti-tTG and EMA) from 11,915 individuals were measured. Data were combined with clinical data and results of duodenal biopsy using a unique Danish personal identification number.
RESULTS: The positive predictive value (PPV) varied according to different combinations of positive CD antibodies, being highest when all antibodies were positive (97.6%). The anti-tTG concentration correlated strongly with EMA positivity, number of additional positive antibodies, and higher PPV. A logistic regression model predicted the probability of later biopsy-proven CD in relation to concentrations of IgA AGA and anti-tTG at initial serological screening.
CONCLUSIONS: The anti-tTG concentration at initial serological CD screening was highly informative in relation to EMA positivity, number of additional CD specific antibodies and PPV. Furthermore, in the high-risk group of patients investigated, the concentrations of anti-tTG and IgA AGA at initial serological screening could accurately predict the probability of future biopsy-proven CD.