In adaptive clinical trials, the conventional confidence interval (CI) for a treatment effect is prone to undesirable properties such as undercoverage and potential inconsistency with the final hypothesis testing decision. Accordingly, as is stated in recent regulatory guidance on adaptive designs, there is the need for caution in the interpretation of CIs constructed during and after an adaptive clinical trial. However, it may be unclear which of the available CIs in the literature are preferable. This paper is the second in a two-part series that explores CIs for adaptive trials. Part I provided a methodological review of approaches to construct CIs for adaptive designs. In this paper (part II), we present an extended case study based around a two-stage group sequential trial, including a comprehensive simulation study of the proposed CIs for this setting. This facilitates an expanded description of considerations around what makes for an effective CI procedure following an adaptive trial. We show that the CIs can have notably different properties. Finally, we propose a set of guidelines for researchers around the choice of CIs and the reporting of CIs following an adaptive design.

翻译：在自适应临床试验中，传统治疗效应置信区间（CI）易出现覆盖率不足以及与最终假设检验结论不一致等不良特性。因此，正如近期自适应设计监管指南所述，需谨慎解读自适应临床试验期间及之后构建的置信区间。然而，现有文献中的各类置信区间孰优孰劣尚不明确。本文是自适应试验置信区间系列研究的第二篇。第一部分系统综述了自适应设计置信区间的构建方法学。本文（第二部分）通过一个两阶段群序贯试验的扩展案例研究，包含针对该场景下所提置信区间的全面模拟分析，深入探讨了构建有效自适应试验后置信区间程序的核心考量因素。研究表明，不同置信区间可能呈现显著差异的特性。最后，我们为研究者提出了一套关于自适应设计后置信区间选择与报告的实施指南。