Department of Family Medicine and Public Health Sciences, Wayne State University, Detroit, Michigan, USA.
Center of Molecular Medicine and Genetics, Wayne State University, Detroit, Michigan, USA.
Stat Med. 2022 Jun 30;41(14):2542-2556. doi: 10.1002/sim.9369. Epub 2022 Apr 19.
Cluster/group randomized controlled trials (CRTs) have a long history in the study of health sciences. CRT is a special type of intervention trial in which a complete group is randomly assigned to a study condition (or intervention). It is typically performed when individual randomization is difficult/impossible without substantial risk of contamination across study arms or prohibitive from the cost or group dynamics point of view. In this article, the aim is to design and analyze four-level longitudinal cluster randomized trials. The main interest here is to study the difference between treatment groups over time for such a four-level hierarchical data structure. This work is motivated by a real-life study for education based HIV prevention. Such trials are not only popular for administrative convenience, ethical considerations, subject compliance, but also help to reduce contamination bias. A random intercept mixed effects linear regression including a time by intervention interaction is used for modeling. Closed form expression of the power function to detect the interaction effect is determined. Sample size equations depend on correlation among schools but not on correlations among classes or students while, the power function depends on the product of number of units at different levels. Optimal allocation of units under a fixed cost by minimizing the expected standardized variance is also determined and are shown to be independent of correlations among units in any level. Results of detailed simulation studies find the theoretical power estimates based on the derived formulae close to the empirical estimates.
群组随机对照试验(CRTs)在医学科学研究中有着悠久的历史。CRT 是一种特殊类型的干预试验,其中一个完整的群组被随机分配到一个研究条件(或干预)中。当个体随机化在研究组之间存在实质性污染风险或从成本或群组动态的角度来看是不可行的情况下,通常会进行 CRT。本文旨在设计和分析四级纵向群组随机试验。主要兴趣在于研究这种四级层次数据结构中随时间变化的治疗组之间的差异。这项工作的动机是基于一项基于教育的艾滋病毒预防的实际研究。此类试验不仅因其行政便利、伦理考虑、受试者依从性而受欢迎,还有助于减少污染偏差。采用包含时间与干预相互作用的随机截距混合效应线性回归来进行建模。确定了检测交互作用的功效的封闭形式表达式。样本量方程取决于学校之间的相关性,但不取决于班级或学生之间的相关性,而功效取决于不同层次上单位的乘积。通过最小化预期标准化方差来确定在固定成本下的最优单位分配,并发现其与任何层次上单位之间的相关性无关。详细的模拟研究结果发现,基于推导公式的理论功效估计值与经验估计值接近。