Antibodies to human recombinant tissue transglutaminase may detect coeliac disease patients undiagnosed by endomysial antibodies

Background: The screening and diagnosis of coeliac disease have been simplified by the advent of new serological tools. Aim: To assess the clinical utility of a newly developed kit for antibodies to human recombinant tissue transglutaminase (hu-anti-tTG) in a large population of patients undergoing intestinal biopsy for suspected intestinal disorders. Methods: We evaluated 426 serum samples from consecutive adult patients (250 from untreated coeliac disease patients and 176 from individuals in whom a diagnosis of coeliac disease had been excluded), obtained at the time of intestinal biopsy. Samples were tested for immunoglobulin A (IgA) hu-anti-tTG by enzyme-linked immunoabsorbent assay, IgA endomysial antibodies (EmA) by indirect immunofluorescence and IgA and IgG antigliadin antibodies by enzyme-linked immunoabsorbent assay. A sub-group of samples was also assessed for a guinea-pig-based anti-tissue transglutaminase. Results: According to the cut-off for hu-anti-tTG, the sensitivity, specificity and positive and negative predictive values were 91%, 96%, 97% and 87%, respectively. Simultaneous determination of EmA showed values of 86%, 100%, 100% and 83% for the same parameters. Although 19 coeliac disease patients (7.6%) were negative for EmA and hu-anti-tTG, both tests rendered superior statistical values to antigliadin antibody tests. At diagnosis, IgA deficiency was detected in 11 patients, but both assays were able to detect samples with mild to moderate deficiency. The comparison of hu-anti-tTG with EmA showed excellent concordance between the tests (kappa statistic, 0.85). Discordance was observed in 20 samples from coeliac disease patients (8%) and in nine samples from controls (5%). Fifteen samples had an EmA-negative but hu-anti-tTG-positive serology, and five showed the converse pattern. Comparison of human recombinant and guinea-pig tests showed concordant results in 96% of cases. Conclusions: The quantitative determination of hu-anti-tTG type IgA using a commercial enzyme-linked immunoabsorbent assay kit was highly sensitive and specific for the detection of coeliac disease. Our results in a large population of patients with a clinical condition suggestive of the disorder demonstrated that the test can be used to detect a substantial number of patients otherwise unrecognized by IgA EmA.