急诊普通外科手术结局工具变量研究中的偏倚激励和异质效应
Biased Encouragements and Heterogeneous Effects in an Instrumental Variable Study of Emergency General Surgical Outcomes
摘要：
我们使用观察数据研究了两种胃肠道疾病（结肠炎和憩室炎）的手术与非手术治疗的疗效。我们部署了一个工具变量设计，外科医生倾向于将其作为一种工具进行操作。假设工具有效性，我们发现，非手术的替代方案可以减少住院时间和并发症的风险，估计影响更大的脓毒症患者比非脓毒症患者。我们的工具的有效性是合理的，但不是铁的，需要一个敏感性分析。IV设计的现有敏感性分析假设效应同质性，由于患者特异性生理学原因，不太可能在此成立。我们开发了一种新的敏感性分析，可容纳任意效应异质性和利用组件可解释的观察功能。我们发现，非脓毒症患者的结果证明更强大的隐藏的偏见，尽管有较小的估计影响。对于非脓毒症患者，两个具有相同观察特征的个体在分配给高倾向手术外科医生的几率上必须相差2.34倍，才能推翻我们关于非手术治疗在缩短住院时间方面的益处的发现。对于脓毒症患者，该值仅为1.64。模拟表明，这种现象可以解释组内异质性的差异。
英文摘要：
We investigate the efficacy of surgical versus non-surgical management for two gastrointestinal conditions, colitis and diverticulitis, using observational data. We deploy an instrumental variable design with surgeons' tendencies to operate as an instrument. Assuming instrument validity, we find that non-surgical alternatives can reduce both hospital length of stay and the risk of complications, with estimated effects larger for septic patients than for non-septic patients. The validity of our instrument is plausible but not ironclad, necessitating a sensitivity analysis. Existing sensitivity analyses for IV designs assume effect homogeneity, unlikely to hold here because of patient-specific physiology. We develop a new sensitivity analysis that accommodates arbitrary effect heterogeneity and exploits components explainable by observed features. We find that the results for non-septic patients prove more robust to hidden bias despite having smaller estimated effects. For non-septic patients, two individuals with identical observed characteristics would have to differ in their odds of assignment to a high tendency to operate surgeon by a factor of 2.34 to overturn our finding of a benefit for non-surgical management in reducing length of stay. For septic patients, this value is only 1.64. Simulations illustrate that this phenomenon may be explained by differences in within-group heterogeneity.
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