Methods for estimating optimal treatment strategies typically assume unlimited access to resources. However, when a health system has resource constraints, such as limited funds, access to medication, or monitoring capabilities, medical decisions must account for competition between individuals in resource usage. The problem of incorporating resource constraints into optimal treatment strategies has been solved for point exposures (1), that is, treatment strategies entailing a decision at just one time point. However, attempts to directly generalize the point exposure solution to dynamic time-varying treatment strategies run into complications. We sidestep these complications by targeting the optimal strategy within a clinically defined subclass. Our approach is to employ dynamic marginal structural models to estimate (counterfactual) resource usage under the class of candidate treatment strategies and solve a constrained optimization problem to choose the optimal strategy for which expected resource usage is within acceptable limits. We apply this method to determine the optimal dynamic monitoring strategy for people living with HIV when resource limits on monitoring exist using observational data from the HIV-CAUSAL Collaboration.

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使用动态边际结构模型估计资源约束下的最佳动态处理策略

估计最佳治疗策略的方法通常假设对资源的无限访问。但是，当卫生系统存在资源限制时，例如资金有限、药物获取或监测能力有限，医疗决策必须考虑到个人之间在资源使用方面的竞争。对于点暴露 (1)，将资源约束纳入最佳治疗策略的问题已得到解决，即治疗策略只需要在一个时间点做出决定。然而，将点暴露解决方案直接推广到动态时变治疗策略的尝试遇到了并发症。我们通过针对临床定义的子类中的最佳策略来回避这些并发症。我们的方法是采用动态边际结构模型来估计候选处理策略类别下的（反事实）资源使用情况，并解决受约束的优化问题以选择预期资源使用在可接受范围内的最优策略。当使用来自 HIV-CAUSAL 协作的观察数据存在监测资源限制时，我们应用这种方法来确定 HIV 感染者的最佳动态监测策略。