The measurement of IgA and IgG transglutaminase antibodies in celiac disease: a comparison with current diagnostic methods

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Abstract
Celiac disease (CD) is an inflammatory disorder of the small intestine induced by cereal prolamins. The demonstration of IgA endomysial antibodies (EMA) is currently the most reliable serological screen for CD. The antigenic target is transglutaminase. The aim of this study was to develop an ELISA assay for the detection of antibodies to transglutaminase (TGA), and to assess the sensitivity and specificity of TGA for the detection of celiac disease against the benchmarks of jejunal biopsy, antigliadin antibodies (AGA) and EMA. Sera from 57 patients with celiac disease were tested for IgA and IgG TGA, IgA EMA, IgA and IgG AGA, and the total IgA level. The sensitivity, specificity, predictive value and concordance of AGA, EMA and TGA were assessed against the gold-standard biopsy result. IgG plus IgA TGA offered 100% sensitivity in CD patients for whom no dietary intervention had been commenced, with a specificity of 61%. The sensitivity of TGA dropped from 100 to 79% after dietary restriction. In patients on no gluten restriction, there was 100% agreement between TGA and EMA, and 100% agreement between TGA and AGA for the IgA isotype. The false-positive rate for TGA was 53% in Down’s syndrome patients and 25% in patients with systemic autoimmune disorders. We conclude that testing for TGA is a reliable diagnostic serology for celiac disease, with improved sensitivity compared with established methods. The results suggest that serial TGA measurements may be a more accurate marker for dietary compliance than AGA, but prospective studies are required.