Antitissue transglutaminase antibodies outside celiac disease

Background: Tissue transglutaminase enzyme-linked immunosorbent assay (tTG-ELISA) has recently been proposed as a simple and fast screening test for celiac disease (CD). The rate of false-positive and false-negative tests with tTG-ELISA, however, has not been definitively established. Therefore, the aim of our study was to investigate anti-tTG antibodies (TGA) not only in untreated patients with CD and in healthy controls, but also in a large group of patients with other autoimmune diseases. Methods: The presence of TGA was investigated in sera from I I I patients with untreated CD, 96 patients with other autoimmune conditions (28 with autoimmune liver disease, 46 with insulin-dependent diabetes mellitus, 10 with inflammatory bowel syndrome, 12 with type I polyglandular syndrome) and from 100 healthy controls using guinea pic, tTG-ELISA (gp-TG/ELISA) and highly purified recombinant human tTG-ELISA (h-TG/ELISA). Western blotting with guinea pig tTG was also performed. Results: Ninety-four patients with CD who tested positive for antiendomysial antibodies (AEA) and one who tested negative for AEA showed antibodies against the gp-TG, Among the controls, 50% of patients with autoimmune liver disease and 6.5% of patients with insulin-dependent diabetes mellitus tested positive with gp-TG/ELISA. Western blotting experiments revealed that the high rate of positive tests observed using ELISA among the control group sera is attributable to impurities in the op-TG preparation. However, h-TG/ELISA tests were positive for the sera from all patients who tested positive for AEA and from one control who tested negative for AEA, whereas h-TG/ELISA tests were negative for all CD patients who tested negative for AEA and for other controls who tested negative for AEA. Conclusions: The frequency of false-negative and false-positive tests represents the major limit to the use of gp-TG/ELISA. However, because h-TG/ELISA is both simple and fast, it could be used in large screening programs for CD.