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Glucosamine for pain in osteoarthritis: why do trial results differ?
Steven C Vlad1, Michael P LaValley, Timothy E McAlindon
1Boston University Medical Center, Boston, Massachusetts 02118, USA. svlad@bu.edu
Arthritis and Rheumatism
|June 30, 2007
Summary
Glucosamine efficacy in osteoarthritis trials varies significantly. Industry involvement and specific glucosamine sulfate preparations are linked to higher reported effect sizes, unlike glucosamine hydrochloride.
Area of Science:
- Rheumatology
- Pharmacology
- Clinical Trials Methodology
Background:
- Investigational trials of glucosamine for osteoarthritis report inconsistent efficacy estimates, hindering definitive conclusions.
- This variability, or heterogeneity, necessitates identifying factors influencing trial outcomes.
Purpose of the Study:
- To identify specific factors that explain the heterogeneity in effect sizes observed across randomized controlled trials of glucosamine for osteoarthritis pain.
- To investigate the influence of study design, subject characteristics, and industry involvement on glucosamine efficacy estimates.
Main Methods:
- A systematic literature search was conducted across multiple databases (Ovid Medline, Cochrane) for randomized, double-blind, placebo-controlled trials of glucosamine for knee or hip osteoarthritis.
- Data extracted included study design features, participant details, and markers of industry involvement (funding, drug supply, authorship).
- Statistical analysis focused on identifying factors explaining differences in effect sizes and changes in heterogeneity measures (I²).
Main Results:
- Fifteen trials met the inclusion criteria, with a summary effect size of 0.35 (95% CI 0.14, 0.56) and substantial heterogeneity (I² = 0.80).
- Industry involvement was associated with significantly higher effect sizes (0.47-0.55) compared to trials without industry involvement (0.05-0.16).
- Glucosamine sulfate showed a higher effect size (0.44) than glucosamine hydrochloride (0.06). Trials using Rottapharm products reported an effect size of 0.55.
Conclusions:
- The heterogeneity in glucosamine trials is statistically significant and not attributable to chance.
- Glucosamine hydrochloride appears ineffective for osteoarthritis pain.
- Higher effect sizes in industry-involved trials suggest potential bias or differences in glucosamine preparations, warranting further investigation into allocation concealment and specific product formulations.