Objective: To determine which test would yield the most useful clinical data in evaluation of irritable bowel syndrome (IBS).
Methods: One hundred ninety-six patients who met the International Congress of Gastroenterology criteria for irritable bowel syndrome were prospectively evaluated with hematological, biochemical, and metabolic laboratory testing, as well as a structural evaluation of the colon.
Results: complete blood count, sedimentation rate (ESR), serum chemistries, thyroid profile, and urinalysis were normal or yielded no useful clinical information. Stool examinations for parasites were also normal. Structural evaluations (barium enema, x-ray, and flexible sigmoidoscopy or colonoscopy) revealed abnormalities, including colon cancer (1), polyps (9), colitis (1), melanosis coli (2), diverticulosis (17), and hemorrhoids (11). Forty-eight subjects (25.8%) had lactose maldigestion confirmed by H2 breath lactose testing. Prior to formal testing, 25 (52%) of these subjects were unaware of the relationship between lactose-containing foods and their symptoms.
Conclusions: 1) ESR, thyroid profiles, and parasite examinations had no diagnostic yield in this study and, without specific clinical indication from history and physical examination, should not be part of the "routine" IBS evaluation. 2) Lactose hydrogen breath testing is encouraged for patients with and without milk intolerance who present with IBS.