Public and Environmental Health Research Unit, London School of Hygiene and Tropical Medicine, London WC1E 7HT, UK.
J Epidemiol Community Health. 2011 Jul;65(7):582-7. doi: 10.1136/jech.2008.082602. Epub 2009 Feb 12.
There has been a recent increase in interest in alternatives to randomisation in the evaluation of public health interventions. We aim to describe specific scenarios in which randomised trials may not be possible and describe, exemplify and assess alternative strategies.
Non-systematic exploratory review.
In many scenarios barriers are surmountable so that randomised trials (including stepped-wedge and crossover trials) are possible. It is possible to rank alternative designs but context will also determine which choices are preferable. Evidence from non-randomised designs is more convincing when confounders are well-understood, measured and controlled; there is evidence for causal pathways linking intervention and outcomes and/or against other pathways explaining outcomes; and effect sizes are large.
Non-randomised trials might provide adequate evidence to inform decisions when interventions are demonstrably feasible and acceptable, and where evidence suggests there is little potential for harm, but caution that such designs may not provide adequate evidence when intervention feasibility or acceptability is doubtful, and where existing evidence suggests benefits may be marginal and/or harms possible.
最近人们对公共卫生干预措施评估中替代随机化的方法产生了浓厚兴趣。我们旨在描述随机试验可能不可行的具体情况，并描述、举例说明和评估替代策略。
非系统性探索性综述。
在许多情况下，障碍是可以克服的，因此可以进行随机试验（包括逐步楔形和交叉试验）。可以对替代设计进行排序，但背景也将决定哪些选择更可取。当混杂因素得到很好的理解、测量和控制时，来自非随机设计的证据更有说服力；有证据表明干预措施和结果之间存在因果关系，或者存在其他解释结果的途径；并且效应量较大。
当干预措施明显可行且可接受，并且证据表明潜在危害较小时，非随机试验可能提供足够的证据来为决策提供信息，但需要谨慎的是，当干预措施的可行性或可接受性存在疑问时，此类设计可能无法提供足够的证据，并且现有证据表明收益可能微不足道，并且/或者可能存在危害。
