P0432 CAN TTG REPLACE SMALL BOWEL BIOPSY TO DIAGNOSE CELIAC DISEASE IN SELECT PEDIATRIC POPULATIONS?

Introduction: The increasingly widespread use of screening tests for celiac disease (CD) has raised the awareness and the number of patients referred for investigation. The current gold standard for the diagnosis of CD is the histological analysis of a small intestinal (SI) biopsy. Commercially available IgA anti-tissue transglutaminase antibody (TTG) screening tests have high sensitivities and specificities using manufacturer recommended cut-off values. We propose that the subgroup of patients with very high TTG titres is positive for CD, a SI biopsy is not always necessary to make the diagnosis and a gluten-free diet should be trialed. If the patient’s symptoms do not improve then a SI biopsy should be performed. Methods: We conducted a retrospective chart review of 104 patients that had both a TTG and SI biopsy at BC Children’s Hospital between September 2000 and October 2003. The biopsies were reviewed by a pathologist blinded to the TTG results and previous biopsy reports. Manufacturer’s recommended and previously validated in hospital TTG value cut-offs were; <20 negative and >=20 positive. Our lab reports individual values from 1 to 100 and >100 using a semi-quantitative ELISA. We used TTG >100 and <20 for cut-offs and suggested biopsying patients with TTG values between 20–100. Results: 59/104 patients were biopsy positive, 14 males and 45 females. 45/104 were negative, 24 males and 21 females. Predispositions to celiac disease included IDDM=14, thyroid disease=4, Down’s syndrome=4, celiac disease in a first degree relative=6 and autoimmune disease in the family=12. Three patients with TTG <20 had positive biopsies, 2 were IgA deficient and 1 had no IgA reported. Predisposition to CD was not related to a TTG >100 or a positive biopsy. Conclusion: By changing the cut-off values for our TTG kit to >100 and <20 and checking for selective IgA deficiency, we found TTG to be highly accurate for celiac disease. If patients do not improve on the gluten-free diet, then they should be investigated with a SI biopsy. Patients with TTG values of 20–100 or <20 with known IgA deficiency need to be biopsied to diagnose CD. This proposal could shorten the time to diagnosis, eliminate the need for some patients to undergo a SI biopsy and save patient and hospital expenses.

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