Placebo therapy in Crohn's disease.

The knowledge of the outcome among patients receiving placebo is important for evaluating the response to therapy, for evaluating the natural history of a disease and for calculating the sample size for future clinical trials. In Crohn's disease placebo has been used in therapeutic trials in every relevant setting: active disease, prevention of relapse after induced medical remission and after surgery and fistulising disease. The analysis of the placebo response shows that in every setting there is a high heterogeneity demonstrating mainly that the selection of patients is not often homogeneous and that the outcome criteria used in the trials is not highly reliable. Better selection of patients and more precise definition of outcome measures are warranted to reduce the heterogeneity among placebo response in clinical trials.