Sven Trelle, MD; Stephan Reichenbach, MD; Peter Jüni, MD
Potential Financial Conflicts of Interest: None disclosed.
Trelle S, Reichenbach S, Jüni P. Chondroitin for Osteoarthritis of the Knee or Hip. Ann Intern Med. 2007;147:884-885. doi: 10.7326/0003-4819-147-12-200712180-00016
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Published: Ann Intern Med. 2007;147(12):884-885.
As correctly pointed out by Dr. Goldberg and colleagues, our meta-analysis was hampered by the limited quality of included trials and the heterogeneity of their results. Therefore, the interpretation of the meta-analysis of all trials was difficult and the investigation of potential sources of heterogeneity mandatory (1). The restriction of the analysis to large-scale, high-quality trials covering 40% of patients was not based on subjective judgment, but on results from stratified analyses and corresponding interaction tests. All explored factors were prespecified before initiating our systematic review. The 3 factors associated with treatment effects—concealment of allocation, intention-to-treat analysis, and sample size—are known to be associated with bias (2, 3). The cutoff of 200 patients used to explore the influence of trial size was specified in a grant proposal submitted to and funded by the Swiss National Research Programme 53 on musculoskeletal health (http://www.nfp53.ch/e_module.cfm?kati=6), which was initiated in 2004 before 4 of the 5 large-scale trials became available. The only trial with more than 200 patients that was already available in 2004 (4) showed a large effect of chondroitin, which was incompatible with the effects found in any of the subsequent large-scale trials. It lacked adequate concealment of allocation, did not have a placebo control group, and failed to perform an intention-to-treat analysis.
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