Definition and classification of irritable bowel syndrome: current consensus and controversies

The symptom-based taxonomy of IBS and other functional bowel disorders is based on defined individual symptoms and the co-occurrence of certain symptoms in individuals. Wording of survey questions to accurately reflect the symptoms can be difficult in English, but accomplishing it for non-English-speakers, especially residents of non-Western societies, is an even greater challenge that needs more attention. The potential for misdiagnosis and inappropriate management, including unnecessary surgery, under-scores the need for wider knowledge of typical IBS symptoms by physicians and the collaboration of primary and specialist physicians in patient care. Even though the evolving symptom classification is as evidence-based as its designers can make it, some arbitrariness is inevitable. Population prevalence rates vary widely, depending on diagnostic criteria and other factors, and further work is needed to determine which individuals detected in surveys consider themselves distressed enough to want medical care and why the remaining people do not feel this need. Clearly, more primary care patients should be studied. Physicians should assess clinical trials critically regarding patient recruitment methods and patient features that could influence whether the results are applicable to their patients. The instability of bowel habit subtypes suggests that relatively few patients should expect relief by taking the same motility-active drug regularly for a long time. Long-term, natural history studies of symptoms and health care use are needed. Discoveries of subtle morphologic pathology and disordered physiology are elucidating IBS pathophysiology further, which some experts believe will lead to a more objective, laboratory-based (organic) diagnosis and more effective therapy. The benefit patients will obtain from supplementing a traditional symptom-based, biopsychosocial approach with such findings remains to be determined. The symptom criteria have had important roles in epidemiological studies and characterizing subjects for clinical trials. Many practitioners, however,do not know the typical symptoms or use the criteria, and investigating how physicians diagnose IBS has received scanty attention. It is unknown how many physicians diagnose IBS by exclusion only after extensively testing patients with typical symptoms and no alarm features, but determining this could have important economic and safety implications. There has been little careful validation of the symptom criteria, especially with primary care patients, and no particular criteria are clearly superior for clinical practice,although the Manning and Rome I criteria have been most evaluated and are less restrictive than the Rome II criteria.