The Manitoba Inflammatory Bowel Disease Cohort Study: prolonged symptoms before diagnosis--how much is irritable bowel syndrome?

BACKGROUND & AIMS: The Manitoba Inflammatory Bowel Disease (IBD) Cohort Study is a population-based prospective cohort study of recently diagnosed IBD (n=396). At enrollment, 162 (41%) indicated gastrointestinal symptom>or=3 years before diagnosis. We aimed to determine whether coexistence of irritable bowel syndrome (IBS) had a role in symptoms before IBD diagnosis.
METHODS: Patients were interviewed about symptoms and investigations before IBD diagnosis. Patients were assessed retrospectively for preexisting IBS.
RESULTS: Of 112 patients interviewed, 58% had Crohn's disease, 37% UC, 3% proctitis, and 2% indeterminant colitis. Symptoms at IBD diagnosis were considered the same (7%), worse (43%), different (20%), or both worse and different (30%) than at initial onset. Mean time between initial symptoms and diagnosis was 11 years (range, 3-48 years). Increasing age at IBD diagnosis correlated with a longer period after initial symptoms and diagnosis of IBD (r=.32, P<.0001). Gender and specific IBD diagnosis had no effect on this time period. Patients were identified as no previous IBS (51%), likely IBS (25%), and possible IBS (24%). Those with likely and possible IBS had a trend toward longer symptom duration before IBD diagnosis than those without IBS (P=.07). Of the total IBD cohort (n=396), considering only those with symptoms for >or=3 years before diagnosis, 14% were considered to have likely or possible IBS.
CONCLUSIONS: These data suggest that older patients and those with likely and possible preexisting IBS are more likely to experience longer symptom duration before diagnosis of IBD. The prevalence rate of IBS was similar to estimated base rates in the general population.