How big should the pilot study for my cluster randomised trial be?
How big should the pilot study for my cluster randomised trial be?
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DOI：
10.1177/0962280215588242
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发表时间：
2016-06-01
影响因子：
2.3
通讯作者：
Kerry, Sally M.
中科院分区：
文献类型：
--
作者：
Eldridge, Sandra M.;Costelloe, Ceire E.;Kerry, Sally M.
目前，人们对为随机对照试验做准备而进行的试点研究很感兴趣。本文重点讨论整群随机试验的外部试点研究的样本量要求。当主要结果是连续的时，我们考虑外部试点研究需要多大规模才能评估输入到主要试验样本量计算的关键参数，并以合理的精度估计比率，例如招募率。我们使用模拟来提供主试验的预期簇数量的分布，这些假设涉及自然簇大小、簇内相关性、主试验中的最终簇大小以及试点阶段做出的各种决策的不同假设。我们选择簇内相关值和试点研究规模来反映文献中常见的报告。我们的结果表明，除非试点研究包括大量集群和个体参与者，否则对主要试验所需样本量的估计可能会向下偏差并且非常不精确。我们的结论是，试点研究通常太小，无法以足够的精度估计主要集群随机试验的样本量所需的参数（例如集群内相关系数），并且太小，无法为招募或随访率等过程指标提供可靠的速率估计。
There is currently a lot of interest in pilot studies conducted in preparation for randomised controlled trials. This paper focuses on sample size requirements for external pilot studies for cluster randomised trials. We consider how large an external pilot study needs to be to assess key parameters for input to the main trial sample size calculation when the primary outcome is continuous, and to estimate rates, for example recruitment rates, with reasonable precision. We used simulation to provide the distribution of the expected number of clusters for the main trial under different assumptions about the natural cluster size, intra-cluster correlation, eventual cluster size in the main trial, and various decisions made at the piloting stage. We chose intra-cluster correlation values and pilot study size to reflect those commonly reported in the literature. Our results show that estimates of sample size required for the main trial are likely to be biased downwards and very imprecise unless the pilot study includes large numbers of clusters and individual participants. We conclude that pilot studies will usually be too small to estimate parameters required for estimating a sample size for a main cluster randomised trial (e.g. the intra-cluster correlation coefficient) with sufficient precision and too small to provide reliable estimates of rates for process measures such as recruitment or follow-up rates.