In Screening For Celiac Disease, Deamidated Gliadin Rarely Predicts Disease When Tissue Transglutaminase Is Normal

Objective: While tissue transglutaminase (tTG) antibodies are the most established serological test for celiac disease, newer deamidated gliadin peptide (DGP) screening tests are increasingly being completed. No pediatric study has systematically assessed the incidence of celiac disease in patients with an isolated positive DGP result. We sought to determine the positive predictive value of DGP serology for biopsy-confirmed celiac disease in pediatric patients with elevated DGP and normal tTG, to help guide clinicians' decision making when screening for this common condition and avoid unnecessary invasive follow-up diagnostic testing. Methods: A multi-center retrospective review of children, from birth to age 18, with isolated DGP IgG positive serology referred to three Canadian centers was completed. The positive predictive value of an isolated elevated DGP result was calculated. Results: Forty patients with DGP positive, tTG negative serology underwent endoscopy with duodenal biopsy. Of these, only 1 patient had biopsy-confirmed celiac disease. This patient was IgA deficient. This yields a positive predictive value of 2.5% (95% CI 0.1–14.7%) for isolated DGP IgG positive serology. Conclusion: In isolation, DGP positive serology has a poor positive predictive value for celiac disease in children, especially in IgA sufficient individuals. Our findings suggest that DGP IgG testing should not be completed as part of the initial screening for celiac disease in the pediatric population as it does not effectively differentiate between individuals with and without the disease. Further research is needed to clarify to role of DGP IgG in children under the age of 2 and those with IgA deficiency. Address correspondence and reprint requests to Dr. Catharine M. Walsh, Highest Academic Degree(s): MD, MEd, PhD, FRCPC, FAAP, The Wilson Centre; and the Division of Gastroenterology, Hepatology and Nutrition, the Learning and Research Institutes, Hospital for Sick Children, Department of Paediatrics, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada M5G 1X8 (e-mail: catharine.walsh@sickkids.ca). Received 16 March, 2018 Accepted 3 July, 2018 Financial Disclosure: The authors have no financial relationships relevant to this article to disclose. Conflicts of Interest and Source of Funding: None to declare © 2018 by European Society for Pediatric Gastroenterology, Hepatology, and Nutrition and North American Society for Pediatric Gastroenterology,

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