Yang Shibing, Lu Juan, Eaton Charles B, Harpe Spencer, Lapane Kate L
Am J Epidemiol. 2015 Sep 15;182(6):520-7. doi: 10.1093/aje/kwv098. Epub 2015 Aug 26.
We sought to explore the impact of intention to treat and complex treatment use assumptions made during weight construction on the validity and precision of estimates derived from inverse-probability-of-treatment-weighted analysis. We simulated data assuming a nonexperimental design that attempted to quantify the effect of statin on lowering low-density lipoprotein cholesterol. We created 324 scenarios by varying parameter values (effect size, sample size, adherence level, probability of treatment initiation, associations between low-density lipoprotein cholesterol and treatment initiation and continuation). Four analytical approaches were used: 1) assuming intention to treat; 2) assuming complex mechanisms of treatment use; 3) assuming a simple mechanism of treatment use; and 4) assuming invariant confounders. With a continuous outcome, estimates assuming intention to treat were biased toward the null when there were nonnull treatment effect and nonadherence after treatment initiation. For each 1% decrease in the proportion of patients staying on treatment after initiation, the bias in estimated average treatment effect increased by 1%. Inverse-probability-of-treatment-weighted analyses that took into account the complex mechanisms of treatment use generated approximately unbiased estimates. Studies estimating the actual effect of a time-varying treatment need to consider the complex mechanisms of treatment use during weight construction.
我们试图探讨治疗意向以及在权重构建过程中对复杂治疗使用情况的假设，对逆概率治疗权重分析所得估计值的有效性和精确性的影响。我们假设采用非实验设计模拟数据，旨在量化他汀类药物对降低低密度脂蛋白胆固醇的效果。通过改变参数值（效应大小、样本量、依从水平、治疗起始概率、低密度脂蛋白胆固醇与治疗起始及持续之间的关联），我们创建了324种情景。使用了四种分析方法：1）假设治疗意向；2）假设复杂的治疗使用机制；3）假设简单的治疗使用机制；4）假设混杂因素不变。对于连续性结局，当存在非零治疗效果且治疗起始后存在不依从情况时，假设治疗意向的估计值向无效值偏倚。起始后继续治疗的患者比例每降低1%，估计的平均治疗效果偏倚就增加1%。考虑复杂治疗使用机制的逆概率治疗权重分析产生的估计值大致无偏。估计随时间变化治疗实际效果的研究，在权重构建过程中需要考虑复杂的治疗使用机制。
