背景:效应的溢出,无论是正面还是负面,从干预到对照组的患者使稳定单位治疗变量假设(SUTVA)无效。SUTVA对于随机并发对照试验(RCCT)的有效因果推断至关重要。外溢性感染预防是介导群体免疫的重要人群水平效应。这种羊群效应,除了任何个人层面的影响,包含在通过基于对比度的技术从RCCT得出的总体效果大小(ES)估计中。这种羊群效应仅表现为对照组感染发生率高于背景的分散度增加。
结果:这里的目的是探索溢出的各个方面以及如何将其可视化和诊断。我用,为了说明,来自190RCCT的数据摘录于13篇Cochrane综述中,对ICU患者预防肺炎的各种抗菌和非抗菌干预措施进行了综述.长期以来,人们一直在这种情况下假设溢出。基于手臂的技术使三种方法能够识别增加的分散,无法从基于对比度的技术中获得,这使得能够诊断基于抗菌药物和非抗菌药物的感染预防RCCT的溢出。这三种方法对肺炎发病率与临床相关范围进行了基准测试,比较对照组与干预组之间肺炎发病率的离散度,可视化摘要接收器操作员特征(SROC)图中的入射离散度。根据这些标准,对并发对照组患者有有害的溢出效应。
结论:基于手臂的技术与基于对比剂的技术导致来自基于抗菌药物的干预措施的汇总RCCT的相反推论,尽管总结ES估计相似。此外,基础对照组风险与ES之间的推断关系为“翻转”。
BACKGROUND: Spillover of effect, whether positive or negative, from intervention to control group patients invalidates the Stable Unit Treatment Variable Assumption (SUTVA). SUTVA is critical to valid causal inference from randomized concurrent controlled trials (RCCT).
Spillover of infection prevention is an important population level effect mediating herd immunity. This herd effect, being additional to any individual level effect, is subsumed within the overall effect size (ES) estimate derived by contrast-based techniques from RCCT\'s. This herd effect would manifest only as increased dispersion among the control group infection incidence rates above background.
RESULTS: The objective here is to explore aspects of
spillover and how this might be visualized and diagnosed. I use, for illustration, data from 190 RCCT\'s abstracted in 13 Cochrane reviews of various antimicrobial versus non-antimicrobial based interventions to prevent pneumonia in ICU patients.
Spillover has long been postulated in this context. Arm-based techniques enable three approaches to identify increased dispersion, not available from contrast-based techniques, which enable the diagnosis of spillover within antimicrobial versus non-antimicrobial based infection prevention RCCT\'s. These three approaches are benchmarking the pneumonia incidence rates versus a clinically relevant range, comparing the dispersion in pneumonia incidence among the control versus the intervention groups and thirdly, visualizing the incidence dispersion within summary receiver operator characteristic (SROC) plots. By these criteria there is harmful
spillover effects to concurrent control group patients.
CONCLUSIONS: Arm-based versus contrast-based techniques lead to contrary inferences from the aggregated RCCT\'s of antimicrobial based interventions despite similar summary ES estimates. Moreover, the inferred relationship between underlying control group risk and ES is \'flipped\'.