Quantification of the placebo response in ulcerative colitis

There is consistently a measurable benefit noted among placebo users in treatment trials of ulcerative colitis (UC). The aim of this study was to define the placebo response in active UC and identify study features that influence the placebo response.

MEDLINE database was searched for placebo-controlled treatment studies of active UC. Data extraction was performed by two reviewers, and one separate investigator reviewed all trials and data extraction before data tabulation. Placebo remission and benefit rates were determined for clinical, endoscopic, and histological outcomes. Synthesis analysis on the weighted proportions from the different studies explored the placebo response as it related to eight study variables.

Thirty-eight of 44 studies identified were included in the analysis. The clinical remission rate was 9.1% (confidence interval [CI], 6.6-11.6) and the benefit rate was 26.7% (CI, 24.1-29.2). Similar rates were observed endoscopically and histologically. The number of study visits (< or =3 vs. >3) modified placebo response as assessed by clinical benefit (P = 0.05), endoscopic remission (P = 0.02), and histological remission (P = 0.04). Other study variables were not significant placebo response modifiers.

In trials of active UC, the placebo remission rate is approximately 10% and the placebo benefit rate is approximately 30%. These rates are consistent regardless of assessment end point. The placebo response is greater in trials with more frequent study visits (more than three).