THE USEFULNESS OF DEAMIDATED GLIADIN PEPTIDE IN SCREENING PEDIATRIC PATIENTS FOR CELIAC DISEASE

Abstract

Abstract BACKGROUND Celiac disease (CD) is an autoimmune enteropathy triggered by gliadin. The gold standard for diagnosis is small bowel biopsy. Screening with serologic markers to identify endoscopic candidates is commonly completed by paediatricians. The most common serologic marker used for screening is IgA anti-Tissue Transglutaminase (TTG) antibodies. Antibodies to deamidated gliadin peptide (DGP) is a newer assay with studies demonstrating a diagnostic performance similar to anti-TTG. In Canada, this assay has been added to many laboratory’s celiac screening panels. There is little evidence however regarding the usefulness of an isolated positive anti-DGP result in paediatric patients and no study has systematically assessed the presence of biopsy proven CD in solely anti-DGP positive paediatric patients. OBJECTIVES We sought to determine the positive predictive value of anti-DGP for biopsy proven CD in paediatric patients with negative TTG IgA testing. DESIGN/METHODS A multi-center retrospective review of children referred to three centers in Ontario, Canada between January 2015 and December 2016 who had isolated anti-IgG DGP positive CD serology was completed. To be included, patients required serology positive for DGP IgG and negative for all other celiac serologic tests, as well as a duodenal biopsy while on a gluten-containing diet. The positive predictive value of isolated anti-DGP was calculated. RESULTS A total of 83 patients were identified with anti-DGP positive, anti-TTG negative serology. Of these, 40 patients underwent endoscopy. Only 1 patient had findings consistent with CD on biopsy (Marsh 3B histology), yielding a positive predictive value of 2.5%. This patient was IgA deficient. Amongst the cohort of IgA sufficient patients (N=25), the positive predictive value of anti-DGP serology was 0%. One additional patient who was IgA sufficient had findings in keeping with Marsh 2 histology, but repeat TTG and DGP testing was negative. Five patients were found to be IgA deficient at the time of serologic testing, 25 were IgA sufficient and 10 did not have a measured IgA. CONCLUSION Isolated positive DGP IgG serology has a poor positive predictive value for CD, especially in IgA sufficient individuals. For this reason, DGP IgG testing should not be completed as part of the initial screening for celiac disease in the paediatric population unless a compelling reason, such as IgA deficiency or age under 2 years, is present, in order to prevent unnecessary invasive follow-up testing and costs to patients and the health care system.