The ICH E9(R1) addendum (2019) proposed principal stratification (PS) as one of five strategies for dealing with intercurrent events. Therefore, understanding the strengths, limitations, and assumptions of PS is important for the broad community of clinical trialists. Many approaches have been developed under the general framework of PS in different areas of research, including experimental and observational studies. These diverse applications have utilized a diverse set of tools and assumptions. Thus, need exists to present these approaches in a unifying manner. The goal of this tutorial is threefold. First, we provide a coherent and unifying description of PS. Second, we emphasize that estimation of effects within PS relies on strong assumptions and we thoroughly examine the consequences of these assumptions to understand in which situations certain assumptions are reasonable. Finally, we provide an overview of a variety of key methods for PS analysis and use a real clinical trial example to illustrate them. Examples of code for implementation of some of these approaches are given in supplemental materials.

翻译：ICH E9(R1)增编(2019年)提出主要分层(PS),作为处理经常事件五个战略之一,因此,了解PS的长处、局限性和假设对于临床试验人员的广泛群体十分重要,在PS总的框架内,在不同研究领域,包括实验和观察研究领域,制定了许多办法,这些不同的应用利用了各种各样的工具和假设,因此,有必要以统一的方式提出这些办法。本辅导的目的有三重。首先,我们提供对PS的连贯和统一说明。第二,我们强调,对PS内部影响的估计取决于强有力的假设,我们彻底审查这些假设的后果,以了解在哪些情况下某些假设是合理的。最后,我们概述了PS分析的各种关键方法,并用一个真正的临床试验实例来说明这些办法。在补充材料中提供了执行其中一些办法的守则的例子。