Diagnostic Yield of Isolated Deamidated Gliadin Peptide Antibody Elevation for Celiac Disease

Serologic testing for celiac disease includes tissue transglutaminase and endomysial antibodies. In addition to these tools, assays for deamidated gliadin peptide antibodies have been shown to have sensitivity and specificity that are comparable to tissue transglutaminase testing, and are increasingly being used for celiac disease testing.

The goal of this study is to evaluate the utility of deamidated gliadin peptide (DGP) testing in the setting of a negative tissue transglutaminase (TTG) IgA test.

We reviewed the records of all patients seen at two U.S. celiac disease referral centers and identified those who had an elevated DGP IgA and/or IgG in the setting of a negative TTG IgA. Of these patients, those who underwent duodenal biopsy while on a gluten-containing diet were included. Patients with prior biopsy-proven celiac disease or prior TTG IgA positivity were excluded. The results of the biopsy were used as the gold standard for celiac disease diagnosis, and patients with villous atrophy (Marsh class 3) on duodenal biopsy were considered to have celiac disease.

Between the two institutions, 84 patients were identified with negative TTG IgA and positive DGP IgA or IgG who also had duodenal biopsies performed while maintaining a gluten-containing diet. Of these patients, 13 patients (15.5%; 95% CI 8.5-25.0%) were found to have celiac disease on duodenal biopsy.

DGP antibody testing can identify cases of celiac disease in TTG-negative individuals, although the low positive predictive value suggests that the yield may be low.