 Despite being one of the most frequent reasons for consultation many patients are undiagnosed. There are no reliable biomarkers. The diagnosis is clinical, based on the Rome III criteria. IBS is characterized by chronic or recurrent abdominal pain associated with changes in bowel frequency and consistency, when other etiologies are excluded. The combination of the Rome III criteria with the absence of alarm symptoms have a sensitivity of 65, specificity of 100, 100 positive predictive value and negative predictive value of 76. 