Study design considerations for irritable bowel syndrome clinical trials

Clinical trials of therapies intended to alleviate symptoms of irritable bowel syndrome (IBS) are prevalent. However, the ideal study design remains elusive since there is no obvious pathophysiological target and no universally accepted endpoint to assess symptom improvement in IBS. The purpose of this paper is to identify and discuss the most problematic issues in the design of clinical trials intended to evaluate the effectiveness of treatments for IBS symptoms. Lack of standardized diagnostic criteria, symptom variability, heterogeneous subject characteristics, large placebo effects, lack of statistical power, inappropriate endpoint selection, and poorly selected study design are the most critical issues that may confound study outcomes in IBS clinical trials.