IgA-class transglutaminase antibodies in evaluating the efficacy of gluten-free diet in coeliac disease.

OBJECTIVE Serum IgA-class tissue transglutaminase antibody has proved effective in screening for coeliac disease. The response to a gluten-free diet has been assessed on the basis of small-intestinal morphology. We investigated whether the tissue transglutaminase antibody test could substitute biopsy in this respect, and whether the test is better than the endomysial antibody test in follow-up. DESIGN Controlled cross sectional, and follow-up study. METHODS Serum IgA-class tissue transglutaminase antibodies and endomysial antibodies were determined in 87 coeliac adults on a gluten-free diet. All underwent small bowel biopsy, and the mucosal morphology was interpreted along with Marsh's grading 0-3. In 30 patients histological and serological data could be analysed before and after adopting the diet; Marsh 3 was considered inadequate mucosal recovery during the diet. RESULTS Of the 87 coeliac patients 27 showed Marsh 3 villous atrophy on gluten-free diet; of these 27, tissue transglutaminase antibody was within normal limits in 16 (59%) and endomysial antibody in 20 (74%). Two (7%) out of 29 with normal mucosa (Marsh 0) had positive tissue transglutaminase antibodies. Six (55%) out of 11 admitting regular dietary lapses remained tissue transglutaminase antibody negative. In the follow-up, serum IgA-class tissue transglutaminase antibody was initially positive in 28 (93%) out of 30 untreated patients; even a significant decrease in tissue transglutaminase antibody did not guarantee mucosal recovery. CONCLUSIONS A substantial number of coeliac patients with negative tissue transglutaminase or endomysial antibodies may still have manifest mucosal villous atrophy. Small bowel biopsy is therefore still necessary to ensure that the gluten-free diet is adequate.