Deng Carolyn, Sidebotham David
Department of Anaesthesia and Perioperative Medicine, Auckland City Hospital, Auckland, New Zealand.
University of Auckland, Auckland, New Zealand.
Clin Trials. 2023 Oct;20(5):473-478. doi: 10.1177/17407745231173058. Epub 2023 May 5.
The sample size calculation is an important step in designing randomised controlled trials. For a trial comparing a control and an intervention group, where the outcome is binary, the sample size calculation requires choosing values for the anticipated event rates in both the control and intervention groups (the effect size), and the error rates. The Difference ELicitation in TriAls guidance recommends that the effect size should be both realistic, and clinically important to stakeholder groups. Overestimating the effect size leads to sample sizes that are too small to reliably detect the true population effect size, which in turn results in low achieved power. In this study, we use the Delphi approach to gain consensus on what the minimum clinically important effect size is for Balanced-2, a randomised controlled trial comparing processed electroencephalogram-guided 'light' to 'deep' general anaesthesia on the incidence of postoperative delirium in older adults undergoing major surgery.
Delphi rounds were conducted using electronic surveys. Surveys were administered to two stakeholder groups: specialist anaesthetists from a general adult department in Auckland City Hospital, New Zealand (Group 1), and specialist anaesthetists with expertise in clinical research, identified from the Australian and New Zealand College of Anaesthetist's Clinical Trials Network (Group 2). A total of 187 anaesthetists were invited to participate (81 from Group 1 and 106 from Group 2). Results from each Delphi round were summarised and presented in subsequent rounds until consensus was reached (>70% agreement).
The overall response rate for the first Delphi survey was 47% (88/187). The median minimum clinically important effect size was 5.0% (interquartile range: 5.0-10.0) for both stakeholder groups. The overall response rate for the second Delphi survey was 51% (95/187). Consensus was reached after the second round, as 74% of respondents in Group 1 and 82% of respondents in Group 2 agreed with the median effect size. The combined minimum clinically important effect size across both groups was 5.0% (interquartile range: 3.0-6.5).
This study demonstrates that surveying stakeholder groups using a Delphi process is a simple way of defining a minimum clinically important effect size, which aids the sample size calculation and determines whether a randomised study is feasible.
样本量计算是设计随机对照试验的重要步骤。对于比较对照组和干预组且结果为二元变量的试验，样本量计算需要为对照组和干预组的预期事件发生率（效应大小）以及错误率选择合适的值。“试验中的差异引出”指南建议，效应大小应既现实又对利益相关者群体具有临床重要性。高估效应大小会导致样本量过小，无法可靠地检测到真实的总体效应大小，进而导致检验效能低下。在本研究中，我们采用德尔菲法就“平衡 - 2”试验的最小临床重要效应大小达成共识，“平衡 - 2”是一项随机对照试验，比较经处理的脑电图引导下的“浅”麻醉与“深”麻醉对接受大手术的老年人术后谵妄发生率的影响。
使用电子调查问卷进行德尔菲轮次调查。调查对象为两个利益相关者群体：新西兰奥克兰市医院普通成人科室的专科麻醉师（第1组），以及从澳大利亚和新西兰麻醉师学院临床试验网络中识别出的具有临床研究专业知识的专科麻醉师（第2组）。总共邀请了187名麻醉师参与（第1组81名，第2组106名）。每轮德尔菲调查的结果进行总结，并在后续轮次中呈现，直至达成共识（>70%的一致性）。
第一次德尔菲调查的总体回复率为47%（88/187）。两个利益相关者群体的最小临床重要效应大小中位数均为5.0%（四分位间距：5.0 - 10.0）。第二次德尔菲调查的总体回复率为51%（95/187）。第二轮后达成共识，第1组74%的受访者和第2组82%的受访者同意中位数效应大小。两组合并的最小临床重要效应大小为5.0%（四分位间距：3.0 - 6.5）。
本研究表明，使用德尔菲法对利益相关者群体进行调查是定义最小临床重要效应大小的一种简单方法，这有助于样本量计算，并确定随机研究是否可行。
