Background & aims: The diagnosis of celiac disease often relies on the anti-tissue transglutaminase (tTG) antibody test. The aim of this study was to evaluate its sensitivity and specificity in clinical practice with the use of commercial laboratories, in which the test characteristics might differ from research laboratories.
Methods: We identified 122 patients with suspected celiac disease who had anti-tTG antibody serologies as well as upper endoscopy with duodenal biopsies. Those with celiac disease were classified as either classic (with diarrhea or other symptoms of malabsorption) or silent (asymptomatic). Biopsies from celiac disease patients were classified as either partial (Marsh IIIA) or total (Marsh IIIB or IIIC) villous atrophy.
Results: The overall sensitivity, specificity, and positive and negative predictive values of the anti-tTG antibody test were 70.6%, 65.0%, 91.1%, and 30.2%, respectively. The sensitivity was 90.0% for patients with total villous atrophy and 42.3% for patients with partial villous atrophy (P < .0001). There were differences in both sensitivity and specificity between the 2 most commonly used commercial laboratories. The sensitivity for Lab #1 was 40.0% versus 86.4% for Lab #2 (P < .0001). The specificity for Lab #1 was 100.0%, and it was 41.7% for Lab #2 (P = .02).
Conclusions: The sensitivity of the anti-tTG antibody in clinical practice is not as high as previously reported in research laboratories. The sensitivity is significantly lower in patients with partial villous atrophy. There is also significant variability in test characteristics among major commercial laboratories in the United States. These results need to be confirmed in prospective studies.