Are IBD patients more likely to have a prior diagnosis of irritable bowel syndrome? Report of a case-control study in the General Practice Research Database

Background: Inflammatory bowel disease (IBD) patients are sometimes first diagnosed with irritable bowel syndrome (IBS), which may be construed as a misdiagnosis. Objective: The objective of this article is to determine if this occurs more than expected by chance. Methods: We conducted a case-control study nested in the General Practice Research Database. We selected incident cases of IBD and up to 10 matched controls for each. We assessed the proportions with IBS recorded prior to the IBD diagnosis and variation by age, sex, and calendar time. We compared proportions affected in fixed time periods and conducted conditional logistic regression to derive odds ratios. Results: The 20, 193 cases were three times as likely as controls to have a prior record of IBS. Fifteen per cent of IBD cases and 5% of controls had IBS coded before diagnosis with 11% having a code for IBS over one year before IBD (cf. 5% of controls) and 6% over five years earlier (cf. 3%). These figures roughly doubled if typical antispasmodic therapies were assumed to represent IBS diagnoses. Conclusion: If excess IBS diagnoses represent misdiagnoses of IBD, our results suggest that about 10% of IBD patients are misdiagnosed and in 3% of cases this may persist for five or more years.