and Aims: The diagnosis of irritable bowel syndrome (IBS) is based mainly on clinical evaluation. The reported incidence of misclassification of significant organic diseases in previously diagnosed IBS patients differs between studies. The aim of this study was to examine the incidence and risk factors for the misclassification of significant organic disease [colon cancer, inflammatory bowel disease (IBD), Celiac disease, and thyroid dysfunction] in a cohort of young patients with symptoms

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... buted to IBS. Methods: In this population-based cohort study, we examined the incidence and risk factors for the diagnosis of a new significant organic diseases in a cohort of 2645 IBS patients. Results: During follow-up, organic disease was diagnosed in 27 subjects (1.03%): IBD in 23, Celiac disease in 2, IBD and Celiac disease in 1, and hypothyroidism in1. The mean interval from the diagnosis of IBS to the diagnosis of an organic disorder was 13.08 ± 8.51 months. Increased symptom severity was the only significant risk factor for the misclassification of an organic disease (hazard ratio, 2.26; 95% confidence interval, 1.01-5.05; P = 0.047). The risk ratio for misclassification of organic diseases in moderate to severe IBS was increased by 2.575 (95% confidence interval, 1.10-6.51; P = 0.027) as compared with mild IBS. Conclusions: The incidence of misclassification of major organic disease in IBS patients was low. Increased symptoms severity was the only significant risk factor for the misclassification of organic disorders. Further gastrointestinal evaluation should be considered in patients with moderate to severe symptoms attributed to IBS.