Positive tissue transglutaminase antibodies with negative endomysial antibodies: Low rate of celiac disease

Background: Screening for celiac disease is based on the sequential evaluation of serologic tests and intestinal biopsy; an optimal screening protocol is still under investigation. The screening policy of one of the main healthcare providers in Israel (Maccabi) consists of measuring total immunoglobulin A and tissue transglutaminase IgA antibodies and confirming positive results by endomysial antibodies. For IgA-deficient patients antigliadin IgG is measured. Objectives: To evaluate the use of tTGA as a first-level screening test in patients suspected of having celiac disease. Methods: The results of tTGA and EMA tests over a 3 month period were obtained from the laboratory computer, Letters were sent to the referring physicians of patients with positive tests, requesting clinical information and small intestinal biopsy results. tTGA was performed using an anti-guinea pig tTG-lgA enzyme-linked immunosorbent assay kit. Results: Overall, 2,505 tTGA tests were performed: 216 (8.6%) were tTGA-positive of which 162 (75%) were EMA-negative (group 1) and 54 (25%) EMA-positive (group 2). Clinical information was obtained for 91 patients in group 1 and 32 in group 2. Small intestinal biopsy was performed in 33 (36%) and 27 patients (84%) in groups 1 and 2, respectively. Celiac disease was diagnosed in 4 biopsies (12%) in group 1 and 23 (85%) in group 2 (P < 0.0001). The positive predictive value was 45% for tTGA and 85% for EMA. Conclusions: Symptomatic patients with positive tTGA and negative EMA have a low rate of celiac disease compared lo those who are tTGA-positive and EMA-positive. Confirmation with EMA is advised when tTGA is performed as a first-level screening for suspected cefiac disease.