Institute of Applied Health Research, University of Birmingham, Birmingham, UK.
Department of Infectious Disease Epidemiology, London School of Hygiene and Tropical Medicine, London, UK.
J Clin Epidemiol. 2021 Oct;138:49-59. doi: 10.1016/j.jclinepi.2021.06.021. Epub 2021 Jun 29.
To describe the prevalence of risks of bias in cluster-randomized trials of individual-level interventions, according to the Cochrane Risk of Bias tool.
Review undertaken in duplicate of a random sample of 40 primary reports of cluster-randomized trials of individual-level interventions.
The most common reported reasons for adopting cluster randomization were the need to avoid contamination (17, 42.5%) and practical considerations (14, 35%). Of the 40 trials all but one was assessed as being at risk of bias. A majority (27, 67.5%) were assessed as at risk due to the timing of identification and recruitment of participants; many (21, 52.5%) due to an apparent lack of adequate allocation concealment; and many due to selectively reported results (22, 55%), arising from a mixture of reasons including lack of documentation of primary outcome. Other risks mostly occurred infrequently.
Many cluster-randomized trials evaluating individual-level interventions appear to be at risk of bias, mostly due to identification and recruitment biases. We recommend that investigators carefully consider the need for cluster randomization; follow recommended procedures to mitigate risks of identification and recruitment bias; and adhere to good reporting practices including clear documentation of primary outcome and allocation concealment methods.
根据 Cochrane 偏倚风险工具，描述个体干预措施的整群随机试验中偏倚风险的发生率。
对个体干预措施的整群随机试验的 40 篇原始报告的随机样本进行了重复审查。
报告采用整群随机化的最常见原因是避免污染（17 项，42.5%）和实际考虑（14 项，35%）。在这 40 项试验中，除了一项之外，其余都被评估为存在偏倚风险。大多数（27 项，67.5%）是由于参与者的识别和招募时机造成的；许多（21 项，52.5%）是由于明显缺乏充分的分配隐藏；还有许多是由于选择性报告结果（22 项，55%），这是由于缺乏主要结局的文档记录等多种原因造成的。其他风险则很少发生。
许多评估个体干预措施的整群随机试验似乎存在偏倚风险，主要是由于识别和招募偏倚所致。我们建议研究者仔细考虑是否需要进行整群随机化；遵循推荐的程序来减轻识别和招募偏倚的风险；并坚持良好的报告实践，包括主要结局和分配隐藏方法的明确文档记录。
