Additional investigations fail to alter the diagnosis of irritable bowel syndrome in subjects fulfilling the Rome Criteria

OBJECTIVE: Irritable bowel syndrome (IBS) is diagnosed by the presence of a constellation of symptoms fulfilling the Manning or Pome Criteria, after e xclusion of organic disease. To exclude other diagnoses that might contribu te to the abdominal pain or bowel symptoms experienced by subjects with IBS , numerous screening algorithms have been advocated, incorporating lactose hydrogen breath tests, thyroid function tests, fecal ova and parasite deter mination, and colonic endoscopy/radiography. The utility of these tests in uncovering alternative diagnoses, other than IBS, was examined in 1452 pati ents. METHODS: Data were combined from two large multinational studies of IBS pat ients. All patients exhibited symptoms meeting the Pome criteria for IBS fo r at least 6 months before study entry. If prior evaluation had been >2 yr previously, patients underwent colonic endoscopy/radiography at study entry . In addition, thyroid function tests, fecal ova and parasite determination , and a lactose hydrogen breath test were performed. RESULTS: Lactose malabsorption was diagnosed in 23% (256/1122) of patients. Colonic abnormalities were detected in 2% (7/306) of patients; in four pat ients, colonic inflammation (n = 3) or obstruction (n = 1) may have contrib uted to symptoms of abdominal pain or altered bowel habits. Abnormal thyroi d-stimulating hormone levels were detected in 6% (67/1209) of patients, of whom half were hypothyroid and half were hyperthyroid. Positive fecal ova a nd parasite tests were noted in 2% (19/1154) of patients. CONCLUSIONS: Examination of screening tests in 1452 patients with an establ ished history of IBS revealed an incidence of lactose malabsorption compara ble to that in the general U.S. population and a low incidence of thyroid d ysfunction, ova and parasite infestation, or colonic pathology. The limited detection rates, added costs, and inconvenience of these tests suggest tha t their routine use in the diagnostic evaluation of established IBS patient s should be scrutinized. (C) 1999 by Am. Cell. of Gastroenterology.