Pragmatic clinical trials evaluate the effectiveness of health interventions in real-world settings. Negative spillover can arise in a pragmatic trial if the study intervention affects how scarce resources are allocated between patients in the intervention and comparison groups. This can harm patients assigned to the control group and lead to overestimation of treatment effect. While this type of negative spillover is often addressed in trials of social welfare and public health interventions, there is little recognition of this source of bias in the medical literature. In this article, I examine what causes negative spillover and how it may have led clinical trial investigators to overestimate the effect of patient navigation, AI-based physiological alarms, and elective induction of labor. I also suggest ways to detect negative spillover and design trials that avoid this potential source of bias.

翻译：实用性临床试验旨在评估健康干预措施在真实世界环境中的有效性。当研究干预措施影响到稀缺资源在干预组与对照组患者之间的分配时，实用性试验中可能出现负溢出效应。这可能对分配到对照组的患者造成伤害，并导致治疗效果被高估。尽管此类负溢出效应在社会福利与公共卫生干预试验中常被探讨，但医学文献对此类偏倚来源的认知仍然有限。本文考察了负溢出的成因，以及它如何导致临床试验研究者高估患者导航、基于人工智能的生理警报和选择性引产的效果；同时提出检测负溢出及设计避免该潜在偏倚来源的试验方法。