Abstract
Introduction: Anti-endomysial antibodies have high specificity (90%) for the presence of coeliac disease, but there are ethical and cost issues associated with using monkey oesophagus for clinical tests. Tissue transglutaminase (tTG) is the main autoantigen recognised by endomysial antibodies and commercial tests have recently become available to measure tTG in serum. Aim: To establish the diagnostic sensitivity, specificity, positive and negative predictive value of IgA anti-tTG in adult clinical practice. Methods: The study comprised 48 patients (mean age 52 years: range 20–86, 31 females) undergoing investigation for possible coeliac disease i. Patients with known coeliac disease were excluded from study. Serum IgA anti-tTG antibody titres were measured quantitatively by an enzyme-linked immunosorbent assay (QuantaLite tTG, Inova Diagnostics, Ca, USA). Samples were classified as negative (<20 units), weakly positive (20–30) or moderate to strongly positive (>30 units). Results: Duodenal biopsies were normal in 40 patients and untreated coeliac disease was diagnosed in the remaining 8 cases. All 8 patients with coeliac disease had moderate to strongly positive anti-tTG antibody titres. In addition, 9 of 40 patients without coeliac disease were anti-tTG antibody titre positive (5 weakly positive, 4 moderate to strongly positive). Overall, IgA antitissue tTG had a diagnostic sensitivity, specificity, positive and negative predictive value of 100%, 78%, 47% and 100% respectively. Conclusion: IgA antibody to tissue transglutaminase appears to be a highly sensitive predictor of adult onset coeliac disease in clinical practice. practice. The relatively high false positive rates for tTG in this material requires further study.