IMPROVING DIAGNOSTIC ACCURACY OF TISSUE TRANSGLUTAMINASE AUTOANTIBODY DETERMINATION IN COELIAC DISEASE

Abstract

40 We hypothesised that a gliadin-transglutaminase interaction might generate other epitopes recognisable by transglutaminase antibodies (TGA) and might enhance diagnostic accuracy of TGA determination for screening coeliac disease. With this aim in mind we developed an IgA ELISA with guinea-pig liver tissue transglutaminase C (Sigma), at concentration of 10 µg/ml in calcium-containing Tris-buffered saline. Sera from 101 patients were tested for TGA: 43 untreated coeliac patients, as defined by a subtotal villous atrophy of duodenal mucosa at histology; 56 controls, who underwent intestinal biopsy because symptoms suggestive of coeliac disease, with a normal duodenal mucosa at histology and negative serum IgA-class human umbilical cord endomysial antibodies. The cut-off limit was calculated as the mean value plus 3 standard deviations of the optical densities obtained in sera from the controls. TGA were positive in sera of 38 untreated patients (sensitivity 88%) and of 2 controls (specificity 96%). The same sera were also tested for TGA after pre-incubation of transglutaminase with gliadin at 37° C for 30 minutes in calcium-containing Tris-buffered saline before coating microplates. TGA were positive in sera of all untreated coeliac patients (sensitivity 100%) and in 1 control (specificity 98%). The average cost of a test is about 1/2 US dollar. Our results suggest that the pre-incubation of transglutaminase with gliadin may improve the diagnostic accuracy of TGA determination which can be a cheap and reliable screening test for coeliac disease.