Methodology State-of-the-art workshop: Choosing the target difference (“effect size”) for a randomised controlled trial

随机对照试验(RCT)被认为是评估比较临床疗效和有效性的最佳研究设计。样本量计算确保了研究有合理的机会实现其预先指定的目标：需要在被偶然误导的可能性(治疗之间没有真正的差异)和即使其中一种治疗确实有效时也无法识别差异的风险之间达成妥协。“目标差异”是RCT旨在可靠地调查的差异的大小。它也通常被称为试验的“效应大小”。关键的问题是，从统计上检测到的特定差异是否具有任何实际意义。从科学和伦理的角度来看，选择适当的目标差异至关重要--指定太小的目标差异可能是对资源的浪费(可能是不道德的)，而太大可能会导致重要的差异被忽视。此外，由此产生的规模过小的研究将不会产生可靠的证据。尽管有许多不同的方法可以选择目标差异，但很少有人经常在实践中使用。该项目将：1.审查现有指导方针；2.确定实践中的关键方法发展或变化；3.确定所需指导方针的范围；4.为选择和报告目标差异(效果大小)制定结构化指导方针。

Randomised controlled trials (RCT) are considered the optimal study design to assess comparative clinical efficacy and effectiveness. A sample size calculation ensures the study has a reasonable chance to achieve its pre-specified objectives: A compromise is required between the possibility of being misled by chance (there is no true difference between treatments) and the risk of not identifying a difference even when one of the treatments is truly superior. The “target difference” is the size of the difference the RCT is designed to reliably investigate. It is also commonly referred to as the trial “effect size”. The critical question is whether a particular difference detected statistically, is of any practical interest. From a scientific and ethical standpoint, selecting an appropriate targeted difference is of crucial importance - specifying too small a target difference could be a wasteful (and perhaps unethical) use of resources, and too large could lead to an important difference being overlooked. Furthermore, the resultant undersized study will not produce reliable evidence.Despite there being many different approaches available to choose the target difference, few are used regularly in practice. The project will: 1. Review the existing guidance; 2. Identify key methodological developments or changes in practice; 3. Determine the scope of the guidance required; 4. Produce structured guidance for choosing and reporting the target difference (effect size)