Abstract
ObjectivesTo review the methodology and reporting of sample size calculations in a contemporary sample of trials in osteoarthritis. Study Design and SettingRandomized trials in hip and/or knee osteoarthritis published in 2016 were identified by searching MEDLINE, Cochrane library, CINAHL, EMBASE, PsycINFO, PEDro, and AMED until March 31, 2017. Data were extracted on study characteristics, methods used to calculate the sample size, and the reporting and justification of components used in the sample size calculation. We attempted to replicate the sample size calculation using the reported information. ResultsThis review included 116 trials. Seventy-eight (67%, n = 78/116) reported a power calculation. Less than a quarter reported all core components of the sample size calculation (21%, n = 16/78). The sample size calculation was only reproducible in 53% of the trials that reported a power calculation (n = 41/78). The replicated calculation produced a sample size over 10% larger than the reported value in 12% of trials (n = 9/78). Insufficient information was reported to allow the sample size calculation to be replicated in a quarter of trials (27%, n = 21/78). ConclusionSample size calculations in trials of hip and knee osteoarthritis are not adequately reported, and the calculation frequently cannot be reproduced.
Highlights
We explored whether recently published osteoarthritis trials poorly reported their sample size calculations
We present the number of studies with a replicated value over 10% or 30% above or below the reported sample size
The follow-up standard deviation was over 30% larger than the value assumed in the sample size calculation in six trials (21%, n 5 6/29), leading to a reduction in power
Summary
The funders had no input into the study design, the collection, analysis and interpretation of data, the writing of the report, or in the decision to submit the article for publication. The views expressed are those of the authors and not necessarily those of the NHS, the NIHR, or the Department of Health
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