Bell Melanie L
Department of Epidemiology and Biostatistics, Mel and Enid Zuckerman College of Public Health, University of Arizona, Tucson, AZ, 85724, USA.
Trials. 2018 Nov 5;19(1):605. doi: 10.1186/s13063-018-2894-y.
Sample size calculations are central to the design of health research trials. To ensure that the trial provides good evidence to answer the trial's research question, the target effect size (difference in means or proportions, odds ratio, relative risk or hazard ratio between trial arms) must be specified under the conventional approach to determining the sample size. However, until now, there has not been comprehensive guidance on how to specify this effect.
This is a commentary on a collection of papers from two important projects, DELTA (Difference ELicitation in TriAls) and DELTA that aim to provide evidence-based guidance on systematically determining the target effect size, or difference and the resultant sample sizes for trials. In addition to surveying methods that researchers are using in practice, the research team met with various experts (statisticians, methodologists, clinicians and funders); reviewed guidelines from funding agencies; and reviewed recent methodological literature. The DELTA guidance stresses specifying important and realistic differences, and undertaking sensitivity analyses in calculating sample sizes. It gives recommendations on how to find appropriate differences, conduct the sample size calculation(s) and how to report these in grant applications, protocols and manuscripts. It is hoped that this will contribute not only to better powered studies, but better reporting and reproducibility and thinking about what a trial should be designed to achieve.
The DELTA researchers have developed a set of comprehensive guidance documents that are welcome and will almost certainly improve the way that trials are designed and reported.
样本量计算是健康研究试验设计的核心内容。为确保试验能提供充分证据以回答试验的研究问题，在传统的样本量确定方法中，必须明确目标效应量（试验组之间均值或比例的差异、比值比、相对风险或风险比）。然而，迄今为止，对于如何确定这个效应量尚无全面的指导。
这是一篇对来自两个重要项目（DELTA，即试验中差异引出项目）的一系列论文的评论，其目的是为系统确定目标效应量、差异以及试验所需的样本量提供循证指导。除了调查研究人员在实际中使用的方法外，研究团队还与各类专家（统计学家、方法学家、临床医生和资助者）进行了会面；查阅了资助机构的指南；并回顾了近期的方法学文献。DELTA指南强调明确重要且现实的差异，并在计算样本量时进行敏感性分析。它针对如何找到合适的差异、进行样本量计算以及如何在资助申请、试验方案和论文中报告这些内容给出了建议。希望这不仅有助于开展效能更高的研究，还能促进更好的报告、可重复性以及对试验应设计达到何种目的的思考。
DELTA研究人员已制定出一套全面的指导文件，这些文件很受欢迎，几乎肯定会改善试验设计和报告的方式。
