Antibodies to recombinant human tissue-transglutaminase in coeliac disease: Diagnostic effectiveness and decline pattern after gluten-free diet

Background/aims: To assess the sensitivity and specificity of IgA and IgG tissue-transglutaminase antibodies assay, the pattern of antibody decline after gluten withdrawal and their modifications with reference to dietary compliance. Subjects: We studied sera from 143 untreated coeliac children and adolescents (8.8 ± 6.1 years), 212 sera from 97 of those patients after gluten withdrawal, and 64 control subjects with non-coeliac intestinal disorders (6.8 ± 4.8 years). Methods: Samples were tested for IgA and IgG class tissue-transglutaminase antibodies by radiobinding assay, using human-derived tissue-transglutaminase, and for IgA anti-endomysium antibodies by indirect immunofluorescence on monkey oesophagus. Results: Untreated coeliac patients had significantly higher titres of IgA and IgG tissue-transglutaminase antibodies than controls (p <0.00001); the diagnostic sensitivity was 95.8% and 99.3%, respectively, and the specificity was 95.3%. Three patients with selective IgA deficiency were positive for IgG tissue-transglutaminase antibodies. The concordance rate between IgA tissue-transglutaminase antibodies and anti-endomysium antibodies was 98.1%. Patients on gluten-free diet showed a significant decrease in IgA and IgG tissue-transglutaminase antibodies with respect to untreated patients (p <0.0001). Tissue-transglutaminase was more sensible than anti-endomysium antibodies to detect small amounts of gluten intake when the compliance was poor. Conclusions: The recombinant human tissue-transglutaminase antibodies assay is a highly sensitive and specific test for diagnosis of coeliac disease, and it is useful in monitoring the compliance to gluten-free diet.