A positive diagnostic strategy is noninferior to a strategy of exclusion for patients with irritable bowel syndrome.

Background & Aims: Guidelines recommend a positive strategy based on symptom criteria to diagnose patients with irritable bowel syndrome (IBS). We conducted a randomized noninferiority trial to determine whether a positive diagnostic strategy is noninferior to a strategy of exclusion, with regard to patients' health-related quality of life (HRQOL).

Methods: We studied 302 patients (18-50 years old) from primary care who were suspected of having IBS and referred by general practitioners. Patients who fulfilled the Rome III criteria for IBS with no alarm signals were randomly assigned to groups assessed by a strategy of exclusion (analyses of blood, stool samples for intestinal parasites, and sigmoidoscopies with biopsies) or a positive strategy (analyses of blood cell count and C-reactive protein). Patients were followed for 1 year. The primary end point was difference in change of HRQOL from baseline to 1 year between groups (on the basis of the Short Form 36 health survey, physical component summary, and noninferiority margin of 3 points). Secondary outcomes were change in gastrointestinal symptoms, satisfaction with management, and use of resources. Findings of diagnostic misclassification were registered.

Results: A positive strategy was noninferior to a strategy of exclusion (difference, 0.64; 95% confidence interval, -2.74 to 1.45). The positive diagnostic strategy had lower direct costs. Each approach had similar effects on symptoms, satisfaction, and subsequent use of health resources. No cases of inflammatory bowel disease, colorectal cancer, or celiac disease were found.

Conclusions: In diagnosing IBS in primary care, use of a positive diagnostic strategy is noninferior to using a strategy of exclusion with regard to the patients' HRQOL. Our findings support the current guideline recommendations.