Dr. LaValley has received an honorarium (less than $10,000) for serving as a member of a Data and Safety Monitoring Board for a GELITA Group study.
Glucosamine for pain in osteoarthritis: Why do trial results differ?
Article first published online: 28 JUN 2007
Copyright © 2007 by the American College of Rheumatology
Arthritis & Rheumatism
Volume 56, Issue 7, pages 2267–2277, July 2007
How to Cite
Vlad, S. C., LaValley, M. P., McAlindon, T. E. and Felson, D. T. (2007), Glucosamine for pain in osteoarthritis: Why do trial results differ?. Arthritis & Rheumatism, 56: 2267–2277. doi: 10.1002/art.22728
- Issue published online: 28 JUN 2007
- Article first published online: 28 JUN 2007
- Manuscript Accepted: 29 MAR 2007
- Manuscript Received: 7 FEB 2007
- NIH. Grant Numbers: AR-47785, AR-07598
Investigators in trials of glucosamine report a range of estimates for efficacy, making conclusions difficult. We undertook this study to identify factors that explain heterogeneity in trials of glucosamine.
We searched for reports of trial results in Ovid Medline, the Cochrane Central Register of Controlled Trials, the Cochrane Database of Systematic Reviews, and proceedings of scientific conferences. We selected reports of randomized, double-blind, placebo-controlled trials of glucosamine for pain from osteoarthritis of the knee or hip. We extracted data regarding features of design, subjects, and markers of industry involvement, including industry funding, whether a drug was supplied by industry, industry participation, and industry-affiliated authorship. We examined which factors best accounted for differences in the effect sizes of studies grouped by these characteristics, and we examined changes in I2, a measure of heterogeneity.
Fifteen trials met our inclusion criteria. The summary effect size was 0.35 (95% confidence interval 0.14, 0.56). I2 was 0.80. Except for allocation concealment, no feature of study design explained this substantial heterogeneity. Summary effect sizes ranged from 0.05 to 0.16 in trials without industry involvement, but the range was 0.47–0.55 in trials with industry involvement. The effect size was 0.06 for trials using glucosamine hydrochloride and 0.44 for trials using glucosamine sulfate. Trials using Rottapharm products had an effect size of 0.55, compared with 0.11 for the rest.
Heterogeneity among trials of glucosamine is larger than would be expected by chance. Glucosamine hydrochloride is not effective. Among trials with industry involvement, effect sizes were consistently higher. Potential explanations include different glucosamine preparations, inadequate allocation concealment, and industry bias.