TGM2 and irritable bowel syndrome: Key evidence: There was low-quality evidence on the role of celiac testing in IBS from a systematic review of 13 observational studies (including 2021 IBS patients and 2978 controls), which found a pooled prevalence rate for positive celiac antibody tests of 1.63% (95% CI, 0.7–3.0) using tissue transglutiminase (TTG) or endomysial IgA (18).