Methodological bias in cluster randomised trials.
Methodological bias in cluster randomised trials.
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DOI：
10.1186/1471-2288-5-10
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发表时间：
2005-03-02
影响因子：
4
通讯作者：
Watson, Judith
中科院分区：
文献类型：
--
作者：
Hahn, Seokyung;Puffer, Suezann;Watson, Judith
背景：整群随机试验易受一系列方法学问题的影响。这些问题并没有被许多研究人员普遍认识到。在本文中，我们讨论的问题，可能会导致在集群trials.METHODS的偏见：我们使用了一个样本的集群随机试验，从最近的审查和髋关节保护的系统评价。我们比较了干预组之间的平均年龄在一个样本的“好”的集群试验与样本的潜在偏见的试验。我们还比较了效果大小，在漏斗图，髋关节保护试验，使用单独的随机化与那些使用集群randomisation.RESULTS：有一种趋势，集群试验，证据方法的偏见，也显示治疗组之间的年龄不平衡。在漏斗图中，我们发现，所有的集群试验显示了一个大的积极影响的髋关节保护器，而单独的随机试验显示了一系列的积极和消极的影响，这表明集群试验可能会产生一个有偏见的估计effect.CONCLUSION：在集群随机试验的设计和执行方法的偏见是频繁的。通过仔细注意聚类试验的设计，可以避免与使用聚类设计相关的一些偏差。第一，如果可能的话，应该采用个人分配。其次，如果需要集群分配，那么理想情况下，参与者应该在集群的随机分配之前被识别。第三，如果无法事先确定，则应使用独立的招募人员招募参与者。
BACKGROUND: Cluster randomised trials can be susceptible to a range of methodological problems. These problems are not commonly recognised by many researchers. In this paper we discuss the issues that can lead to bias in cluster trials.METHODS: We used a sample of cluster randomised trials from a recent review and from a systematic review of hip protectors. We compared the mean age of participants between intervention groups in a sample of 'good' cluster trials with a sample of potentially biased trials. We also compared the effect sizes, in a funnel plot, between hip protector trials that used individual randomisation compared with those that used cluster randomisation.RESULTS: There is a tendency for cluster trials, with evidence methodological biases, to also show an age imbalance between treatment groups. In a funnel plot we show that all cluster trials show a large positive effect of hip protectors whilst individually randomised trials show a range of positive and negative effects, suggesting that cluster trials may be producing a biased estimate of effect.CONCLUSION: Methodological biases in the design and execution of cluster randomised trials is frequent. Some of these biases associated with the use of cluster designs can be avoided through careful attention to the design of cluster trials. Firstly, if possible, individual allocation should be used. Secondly, if cluster allocation is required, then ideally participants should be identified before random allocation of the clusters. Third, if prior identification is not possible, then an independent recruiter should be used to recruit participants.