BACKGROUND/AIMS The stepped-wedge cluster randomized trial (SW-CRT), in which clusters are randomized to a time at which they will transition to the intervention condition - rather than a trial arm - is a relatively new design. SW-CRTs have additional design and analytical considerations compared to conventional parallel arm trials. To inform future methodological development, including guidance for trialists and the selection of parameters for statistical simulation studies, we conducted a review of recently published SW-CRTs. Specific objectives were to describe (1) the types of designs used in practice, (2) adherence to key requirements for statistical analysis, and (3) practices around covariate adjustment. We also examined changes in adherence over time and by journal impact factor. METHODS We used electronic searches to identify primary reports of SW-CRTs published 2016-2022. Two reviewers extracted information from each trial report and its protocol, if available, and resolved disagreements through discussion. RESULTS We identified 160 eligible trials, randomizing a median (Q1-Q3) of 11 (8-18) clusters to 5 (4-7) sequences. The majority (122, 76%) were cross-sectional (almost all with continuous recruitment), 23 (14%) were closed cohorts and 15 (9%) open cohorts. Many trials had complex design features such as multiple or multivariate primary outcomes (50, 31%) or time-dependent repeated measures (27, 22%). The most common type of primary outcome was binary (51%); continuous outcomes were less common (26%). The most frequently used method of analysis was a generalized linear mixed model (112, 70%); generalized estimating equations were used less frequently (12, 8%). Among 142 trials with fewer than 40 clusters, only 9 (6%) reported using methods appropriate for a small number of clusters. Statistical analyses clearly adjusted for time effects in 119 (74%), for within-cluster correlations in 132 (83%), and for distinct between-period correlations in 13 (8%). Covariates were included in the primary analysis of the primary outcome in 82 (51%) and were most often individual-level covariates; however, clear and complete pre-specification of covariates was uncommon. Adherence to some key methodological requirements (adjusting for time effects, accounting for within-period correlation) was higher among trials published in higher versus lower impact factor journals. Substantial improvements over time were not observed although a slight improvement was observed in the proportion accounting for a distinct between-period correlation. CONCLUSIONS Future methods development should prioritize methods for SW-CRTs with binary or time-to-event outcomes, small numbers of clusters, continuous recruitment designs, multivariate outcomes, or time-dependent repeated measures. Trialists, journal editors, and peer reviewers should be aware that SW-CRTs have additional methodological requirements over parallel arm designs including the need to account for period effects as well as complex intracluster correlations.

中文翻译：

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遵守阶梯楔形整群随机试验设计和分析的关键建议：2016-2022 年发表的试验综述。

背景/目的 阶梯楔形聚类随机试验 (SW-CRT) 是一种相对较新的设计，其中聚类被随机分配到将过渡到干预条件的时间，而不是试验组。与传统的平行臂试验相比，SW-CRT 有额外的设计和分析考虑。为了为未来的方法学发展提供信息，包括对试验者的指导和统计模拟研究参数的选择，我们对最近发表的 SW-CRT 进行了审查。具体目标是描述（1）实践中使用的设计类型，（2）遵守统计分析的关键要求，以及（3）围绕协变量调整的实践。我们还研究了依从性随时间和期刊影响因子的变化。方法 我们使用电子检索来识别 2016-2022 年发布的 SW-CRT 的主要报告。两名评审员从每份试验报告及其方案（如果有）中提取信息，并通过讨论解决分歧。结果我们确定了 160 项符合条件的试验，将 11 (8-18) 个簇的中位数 (Q1-Q3) 随机化为 5 (4-7) 个序列。大多数（122 个，76%）是横截面的（几乎都是连续招募的），23 个（14%）是封闭队列，15 个（9%）是开放队列。许多试验具有复杂的设计特征，例如多重或多变量主要结局（50%，31%）或时间依赖性重复测量（27%，22%）。最常见的主要结局类型是二元的（51%）；连续结果不太常见（26%）。最常用的分析方法是广义线性混合模型（112，70%）；广义估计方程的使用频率较低 (12, 8%)。在 142 项少于 40 个聚类的试验中，只有 9 个 (6%) 报告使用了适合少数聚类的方法。统计分析明确调整了 119 项 (74%) 中的时间效应、132 项 (83%) 中的簇内相关性以及 13 项 (8%) 中明显的周期间相关性。协变量被纳入 82 例（51%）主要结果的主要分析中，并且最常见的是个体层面的协变量；然而，明确且完整的协变量预先指定并不常见。在高影响因子期刊上发表的试验与在低影响因子期刊上发表的试验相比，对一些关键方法学要求（调整时间效应、考虑期内相关性）的遵守程度更高。尽管观察到明显的期间间相关性的比例略有改善，但并未观察到随着时间的推移出现实质性改善。结论 未来的方法开发应优先考虑具有二元或事件时间结果、少量聚类、连续招募设计、多变量结果或时间依赖性重复测量的 SW-CRT 方法。试验者、期刊编辑、