The Large Sample Bounds on the Principal Strata Effect with Application to a Prostate Cancer Prevention Trial
The Large Sample Bounds on the Principal Strata Effect with Application to a Prostate Cancer Prevention Trial
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DOI：
10.1515/1557-4679.1365
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发表时间：
2012-01-01
影响因子：
1.2
通讯作者：
Chiba, Yasutaka
中科院分区：
文献类型：
--
作者：
Chiba, Yasutaka
随机化后选择偏倚和死亡截断的问题可能出现在随机化临床试验中;例如，在癌症预防试验中，对于未患癌症的个体，诸如癌症严重程度的结果是不确定的。将分析限制在随机化后选择的亚群可能会导致偏倚的结局比较。处理这些问题的一种方法是考虑主要的分层效应（PSE，或等同的幸存者平均因果效应）。PSE定义为治疗对任一治疗组中选择的亚群结局的影响。不幸的是，在没有识别假设的情况下，通常无法估计PSE;但是，可以使用确定性因果模型推导出界限。在本文中，我们提出了一些假设，推导出窄宽度的界限。这些假设和界限与Zhang和Rubin（2003）介绍的不同，使用来自随机前列腺癌预防试验的数据进行说明。
Issues of post-randomization selection bias and truncation-by-death can arise in randomized clinical trials; for example, in a cancer prevention trial, an outcome such as cancer severity is undefined for individuals who do not develop cancer. Restricting analysis to a subpopulation selected after randomization can give rise to biased outcome comparisons. One approach to deal with such issues is to consider the principal strata effect (PSE, or equally, the survivor average causal effect). PSE is defined as the effect of treatment on the outcome among the subpopulation that would have been selected under either treatment arm. Unfortunately, the PSE cannot generally be estimated without the identifying assumptions; however, the bounds can be derived using a deterministic causal model. In this paper, we propose a number of assumptions for deriving the bounds with narrow width. The assumptions and bounds, which differ from those introduced by Zhang and Rubin (2003), are illustrated using data from a randomized prostate cancer prevention trial.