The randomised trial is the preferred study design for evaluating the effectiveness and safety of interventions. Yet such trials can be prohibitively expensive, unethical, or take too long. When it is not possible to carry out a randomised trial, observational data can be used to answer similar questions. Here, we describe the process of using observational data to emulate a target trial, which applies the study design principles of randomised trials to observational studies that aim to estimate the causal effect of an intervention. The target trial provides a formal framework to help avoid self-inflicted biases common to observational studies. Observational studies can provide evidence on the effectiveness of interventions when randomised trials are not feasible because they are expensive, unethical, or take too long. Causal inference using observational data is, however, challenging; not only are observational studies prone to confounding bias due to the lack of randomisation, but incorrect study design choices (such as the specification of the start of follow-up) can also cause self-inflicted biases.1 Such study design flaws can be overcome by first designing a hypothetical randomised trial—the target trial—that would answer the question of interest, then emulating this target trial using the available observational data and appropriate methodology.23 The first step is to specify the protocol of the trial that ideally would have been conducted, within the constraints of the available observational data. Several elements are considered at this stage245: eligibility criteria, treatment strategies, assignment procedures, outcome(s), follow-up, causal contrasts of interest (eg, …

中文翻译：

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目标试验模拟：将随机试验原则应用于观察性研究

随机试验是评估干预措施的有效性和安全性的首选研究设计。然而，此类试验可能过于昂贵、不道德或耗时过长。当无法进行随机试验时，可以使用观察数据来回答类似问题。在这里，我们描述了使用观察数据模拟目标试验的过程，该过程将随机试验的研究设计原则应用于旨在估计干预措施的因果效应的观察性研究。目标试验提供了一个正式的框架，以帮助避免观察性研究中常见的自我造成的偏见。当随机试验不可行时，观察性研究可以提供干预有效性的证据，因为它们昂贵、不道德或耗时太长。然而，使用观察数据进行因果推理具有挑战性。不仅观察性研究由于缺乏随机性而容易产生混杂偏倚，而且不正确的研究设计选择（例如随访开始的规范）也可能导致自我造成的偏倚。 1 此类研究设计缺陷是可以克服的首先设计一个假设的随机试验——目标试验——来回答感兴趣的问题，然后使用可用的观察数据和适当的方法来模拟这个目标试验。 23 第一步是指定理想的试验方案在现有观测数据的限制下进行。在这个阶段考虑了几个要素245：资格标准、治疗策略、分配程序、结果、随访、