IngentaConnect The placebo effect in irritable bowel syndrome trials: a meta-ana...

Authors: patel, s. m.¹; stason, w. b.²; legedza, a.; ock, s. m.³; kaptchuk, t. j.³; conboy, l.³; canenguez, k.¹; park, j. k.³; kelly, e.¹; jacobson, e.³; kerr, c. e.³; lembo, a. j.¹

Source: Neurogastroenterology and Motility, Volume 17, Number 3, June 2005 , pp. 332-340(9)

Publisher: Blackwell Publishing

Abstract:

Background:

Despite the apparent high placebo response rate in randomized placebo-controlled trials (RCT) of patients with irritable bowel syndrome (IBS), little is known about the variability and predictors of this response. Objectives:

To describe the magnitude of response in placebo arms of IBS clinical trials and to identify which factors predict the variability of the placebo response. Methods:

We performed a meta-analysis of published, English language, RCT with 20 or more IBS patients who were treated for at least 2 weeks. This analysis is limited to studies that assessed global response (improvement in overall symptoms). The variables considered as potential placebo modifiers were study design, study duration, use of a run-in phase, Jadad score, entry criteria, number of office visits, number of office visits/study duration, use of diagnostic testing, gender, age and type of medication studied. Findings:

Forty-five placebo-controlled RCTs met the inclusion criteria. The placebo response ranged from 16.0 to 71.4% with a population-weighted average of 40.2%, 95% CI (35.9–44.4). Significant associations with lower placebo response rates were fulfilment of the Rome criteria for study entry (P = 0.049) and an increased number of office visits (P = 0.026). Conclusions:

Placebo effects in IBS clinical trials measuring a global outcome are highly variable. Entry criteria and number of office visits are significant predictors of the placebo response. More stringent entry criteria and an increased number of office visits appear to independently decrease the placebo response.

Keywords: irritable bowel syndrome; meta-analysis; placebo

Document Type: Research article

DOI: 10.1111/j.1365-2982.2005.00650.x

Affiliations: 1: Division of Gastroenterology, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, MA, USA 2: Division of Gastroenterology, Department of Medicine, Harvard School of Public Health, Harvard, MA, USA 3: Division of Gastroenterology, Department of Medicine, Osher Institute, Harvard Medical School, Boston, MA, USA

The full text electronic article is available for purchase. You will be able to download the full text electronic article after payment.

$50.39 plus tax

The placebo effect in irritable bowel syndrome trials: a meta-analysis