The burden of illness of irritable bowel syndrome
IBS is a prevalent and expensive condition that is associated with a significantly impaired health-related quality of life (HRQOL) and reduced work productivity. Based on strict criteria, 7 to 10 percent of people have IBS worldwide. Community-based data indicate that diarrhea-predominant IBS (IBS-D) and mixed IBS (IBS-M) subtypes are more prevalent than constipation-predominant IBS (IBS-C), and that switching among subtype groups may occur. IBS is 1.5 times more common in women than in men, is more common in lower socioeconomic groups, and is more commonly diagnosed in patients younger than 50 years of age. Patients with IBS visit the doctor more frequently, use more diagnostic tests, consume more medications, miss more workdays, have lower work productivity, are hospitalized more frequently, and consume more overall direct costs than patients without IBS. Resource utilization is highest in patients with severe symptoms, and poor HRQOL. Treatment decisions should be tailored to the severity of each patient's symptoms and HRQOL decrement.
The utility of diagnostic criteria in irritable bowel syndrome
IBS is defined by abdominal pain or discomfort that occurs in association with altered bowel habits over a period of at least three months. Individual symptoms have limited accuracy for diagnosing IBS and, therefore, the disorder should be considered as a symptom complex. Although no symptom-based diagnostic criteria have ideal accuracy for diagnosing IBS, traditional criteria, such as Kruis and Manning, perform at least as well as Rome I criteria; the accuracy of Rome II and Rome III criteria has not been evaluated.
The role of alarm features in the diagnosis of IBS
Overall, the diagnostic accuracy of alarm features is disappointing. Rectal bleeding and nocturnal pain offer little discriminative value in separating patients with IBS from those with organic diseases. Whereas anemia and weight loss have poor sensitivity for organic diseases, they offer very good specificity. As such, in patients who fulfill symptom-based criteria of IBS, the absence of selected alarm features, including anemia, weight loss, and a family history of colorectal cancer, inflammatory bowel disease, or celiac sprue, should reassure the clinician that the diagnosis of IBS is correct.
The role of diagnostic testing in patients with IBS symptoms
Routine diagnostic testing with complete blood count, serum chemistries, thyroid function studies, stool for ova and parasites, and abdominal imaging is not recommended in patients with typical IBS symptoms and no alarm features because of a low likelihood of uncovering organic disease. Routine serologic screening for celiac sprue should be pursued in patients with IBS-D and IBS-M. Lactose breath testing can be considered when lactose maldigestion remains a concern despite dietary modification. Currently, there are insufficient data to recommend breath testing for small intestinal bacterial overgrowth in IBS patients. Because of the low pretest probability of Crohn's disease, ulcerative colitis, and colonic neoplasia, routine colonic imaging is not recommended in patients younger than 50 years of age with typical IBS symptoms and no alarm features. Colonoscopic imaging should be performed in IBS patients with alarm features to rule out organic diseases and in those over the age of 50 years for the purpose of colorectal cancer screening. When colonoscopy is performed in patients with IBS-D, obtaining random biopsies should be considered to rule out microscopic colitis.
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