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November 7, 2001

A Meta-analysis of Hormone Replacement Therapy for Fracture Prevention

Author Affiliations

Stephen J.LurieMD, PhD, Senior EditorIndividualAuthorJody W.ZylkeMD, Contributing EditorIndividualAuthor

JAMA. 2001;286(17):2096-2097. doi:10.1001/jama.286.17.2091

To the Editor: In the "Results" section of their meta-analysis of trials of hormone replacement therapy (HRT) for preventing nonvertebral fractures, Drs Torgerson and Bell-Syer1 report that 15 of the 20 trials carried out double blinding, and 9 of these reported the methods used. In the "Methods" section and in the Abstract, however, they instead refer to "concealment allocation." The authors have thus confused 2 quite different concepts. Double-blinding, in which neither caregivers nor trial participants know which treatment is received, is aimed at eliminating performance and assessment bias.2 By contrast, allocation concealment protects the person from knowledge of the upcoming treatments, and protects against selection bias,2,3 Failure to conceal is clearly associated with biased estimates of treatment effect.4 Unlike double-blinding, allocation concealment is always possible.3