Are positive serum-IgA-tissue-transglutaminase antibodies enough to diagnose coeliac disease without a small bowel biopsy? Post-test probability of coeliac disease

Background: It has been suggested that high titres of tTG are associated with elevated positive predictive values (PPV) for celiac disease. However, the PPV of a strongly positive tTG will depend on the celiac disease prevalence in the different risk groups of the disease Aims: To assess the PPV of a strongly positive tTG for celiac disease. In addition, to calculate the post-test probability for celiac disease of a strongly positive tTG in a setting of routine clinical practice. Methods: 145 consecutive celiac disease patients with positive tTG, and with a small bowel biopsy were included. The PPV for different cut-off points of tTG levels for the diagnosis of celiac disease was assessed. In addition, the cut-offs associated with higher PPV were used to calculate the positive likelihood ratio. A simulation in a setting of routine clinical practice was performed to calculate the post-test probability of celiac disease. Results: No cut-off level was associated with a PPV of 100%. A cut-off of 80 U/mL (11.4 x upper normal limit) was associated with the higher PPV value of 98.6%. In the most frequent clinical situations, which in general have a pre-test probability <10%, the post-test probability after having a strongly positive tTG was 90% or less. Conclusions: A strongly positive tTG should not be enough to diagnose celiac disease in the most frequent clinical situations, small bowel biopsy remaining as the gold standard in these cases. (C) 2012 European Crohn's and Colitis Organisation. Published by Elsevier B.V. All rights reserved.