School of Public Health and Preventive Medicine, Monash University, Melbourne, Victoria, Australia.
Centre for Primary Care and Public Health, Queen Mary University of London, London, UK.
Stat Med. 2022 Aug 15;41(18):3627-3641. doi: 10.1002/sim.9438. Epub 2022 May 21.
Stepped wedge designs are an increasingly popular variant of longitudinal cluster randomized trial designs, and roll out interventions across clusters in a randomized, but step-wise fashion. In the standard stepped wedge design, assumptions regarding the effect of time on outcomes may require that all clusters start and end trial participation at the same time. This would require ethics approvals and data collection procedures to be in place in all clusters before a stepped wedge trial can start in any cluster. Hence, although stepped wedge designs are useful for testing the impacts of many cluster-based interventions on outcomes, there can be lengthy delays before a trial can commence. In this article, we introduce "batched" stepped wedge designs. Batched stepped wedge designs allow clusters to commence the study in batches, instead of all at once, allowing for staggered cluster recruitment. Like the stepped wedge, the batched stepped wedge rolls out the intervention to all clusters in a randomized and step-wise fashion: a series of self-contained stepped wedge designs. Provided that separate period effects are included for each batch, software for standard stepped wedge sample size calculations can be used. With this time parameterization, in many situations including when linear models are assumed, sample size calculations reduce to the setting of a single stepped wedge design with multiple clusters per sequence. In these situations, sample size calculations will not depend on the delays between the commencement of batches. Hence, the power of batched stepped wedge designs is robust to unexpected delays between batches.
阶梯式楔形设计是一种越来越流行的纵向群组随机试验设计变体，以随机但逐步的方式在群组中推出干预措施。在标准的阶梯式楔形设计中，关于时间对结果的影响的假设可能要求所有群组同时开始和结束试验参与。这将需要在任何群组开始进行阶梯式楔形试验之前，在所有群组中都有伦理批准和数据收集程序。因此，尽管阶梯式楔形设计对于测试许多基于群组的干预措施对结果的影响非常有用，但在试验开始之前可能会有很长的延迟。在本文中，我们介绍了“分批”阶梯式楔形设计。分批阶梯式楔形设计允许群组分批开始研究，而不是一次性全部开始，从而允许交错的群组招募。与阶梯式楔形设计一样，分批阶梯式楔形设计以随机和逐步的方式将干预措施推广到所有群组中：一系列独立的阶梯式楔形设计。只要为每个批次单独包含时期效果，就可以使用标准阶梯式楔形样本量计算软件。使用此时间参数化，在许多情况下，包括假设线性模型的情况，样本量计算简化为具有多个序列的单个阶梯式楔形设计。在这些情况下，样本量计算将不依赖于批次之间的延迟。因此，分批阶梯式楔形设计的功效对批次之间的意外延迟具有鲁棒性。
