Lack of Utility of Anti-tTG IgG to Diagnose Celiac Disease When Anti-tTG IgA Is Negative.

Abstract

Guidelines for diagnosing celiac disease (CD) recommend initial testing with a highly sensitive serologic test for anti-tissue transglutaminase immunoglobulin A antibodies (tTG IgA). When the probability of CD is high, IgA deficiency should be considered. The 2 approaches to address this include measuring "both tTG IgA and tTG IgG" or measuring "total IgA." We aim to assess the utility of an isolated positive tTG IgG result in diagnosing CD. We conducted a retrospective review of patients undergoing serologic testing for CD from January 1997 to June 2014. Patients with positive tTG IgG and negative tTG IgA were included. Moreover, all patients who had any other positive CD-specific serologic findings were excluded. Demographics, clinical presentation, tests, and biopsy results were recorded. The indication for checking celiac serology was gastrointestinal symptoms in 172 of 233 patients, iron deficiency anemia in 12, and high-risk screening in 48. Small bowel biopsy was performed in 178 patients (77%); 160 had normal results and 18 had histologic changes suggestive of enteropathy. Nine patients had increased intraepithelial lymphocytes, and 9 had partial villous atrophy. Only 6 cases of CD were, however, confirmed. The utility of isolated tTG IgG in diagnosis of CD was low at 3% (6/178). In this cohort of patients, the utility of isolated tTG IgG in diagnosing CD was low at 3%.