Case–control study of the concurrence of coeliac disease with inflammatory bowel disease

Previous studies suggested that inflammatory bowel disease (IBD) is associated with an increased prevalence of comorbid coeliac disease. Our case-control study aimed to test this association using a large histopathology database.The Inform Diagnostics database is a repository of histopathologic records from patients distributed throughout the United States. In a case-control study among patients with bidirectional endoscopy, we compared the occurrence of coeliac disease in case subjects with IBD or microscopic colitis (MC) and control subjects without inflammatory colitis, calculating odds ratios (OR) and their 95% confidence intervals (CI) adjusted to the varying age, gender and ethnic distributions of case and control subjects.The study population was split into 12,816 IBD cases and 6486 MC cases, who were compared to 345,733 control subjects without colitis. A total of 2892 patients were diagnosed with coeliac disease. Of 12,816 IBD patients, 57 patients (0.4%) harboured coeliac disease compared to 0.7% (2548/345,733) in the control population. The prevalence of coeliac disease among MC patients was 4.4% (288/6486). The corresponding ORs were significantly decreased in IBD (OR: 0.50, CI: 0.38-0.64) and significantly increased in MC patients (6.78, 5.96-7.69). Further stratification of the case populations into subtypes of IBD (Crohn's disease or ulcerative colitis) and MC (collagenous or lymphocytic colitis) similarly revealed significantly decreased and increased ORs for each subtype.The previously reported positive association between coeliac disease and IBD may have been possibly biased by the inclusion of MC cases in the IBD patient population.