Antibodies to deamidated gliadin peptide in diagnosis of coeliac disease

Abstract

Introduction: In recent years, testing for the presence of deamidated gliadin peptide (DGP) antibodies has been introduced to clinical practice both to evaluate patients suspected of coeliac disease and the response to glutenfree diet. However, an adjunctive role for DGP antibodies complementing the widely used tissue transglutaminase (tTG) antibodies for diagnosis has not been confirmed. This study aimed to evaluate whether DGP antibody status could be used to differentiate between patients with and without coeliac disease, prior to histological confirmation. Methods: A total of 79 patients at the Canberra Hospital between August 2014 and December 2015 that had available DGP serology and duodenal biopsies at diagnosis were used to calculate sensitivity and specificity. Detailed demographic and clinical characteristics were obtained on 38 patients with positive tTG and negative or positive DGP serology but not yet diagnosed with coeliac disease when the serology was performed. Demographic information (age, sex, ethnicity, alcohol and smoking status) and clinical characteristics (coeliac disease diagnosis, family and personal history of autoimmune diseases, symptomatology, duodenal biopsy result, anti-endomysial (EMA) and DGP antibody serology) were retrospectively retrieved from medical records. The DGP positive and negative groups were compared using Fisher exact tests and t-tests. Results: The sensitivity and specificity of DGP serology were 71% and 98%, respectively. Only one patient with positive tTG and DGP serology had negative duodenal biopsies. The 38 selected patients with positive tTG serology had a mean age of 25.6 years (SD = 21.1), and 68.4% of them were females. Compared with the DGP negative group, DGP positive patients were younger (19.9 vs 38.9 years old, t (18.604) = 2.419, p = 0.026), more likely to be female (85.0% vs 38.5%, p = 0.009), have a confirmed coeliac diagnosis (85.0% vs 15.4%, p<0.001), present with classical coeliac symptoms (85.0% vs 38.5%, p = 0.009) and have detected anti-EMA (100% vs 15.4%, p<0.001). No significant differences were found in terms of ethnicity, smoking and alcohol status, family and past history of autoimmune disease. Conclusions: DGP assays can complement tTG assays to identify coeliac patients with classical symptomatology. In our study, only a single patient was found to have a negative biopsy following positive result for both tTG and DGP serology. This supports the hypothesis that a combination of tTG and DGP serology may obviate the need for duodenal biopsies in those presenting with classical coeliac disease symptoms, but further study is required. Show more