EVALUATING COSTS WITH UNMEASURED CONFOUNDING: A SENSITIVITY ANALYSIS FOR THE TREATMENT EFFECT

• 成果类型: Article
• 署名作者: Handorf, Elizabeth A.; Bekelman, Justin E.; Heitjan, Daniel F.; Mitra, Nandita
• 署名单位: Pennsylvania Commonwealth System of Higher Education (PCSHE); Temple University; Fox Chase Cancer Center; University of Pennsylvania; University of Pennsylvania
• 刊物名称: ANNALS OF APPLIED STATISTICS
• ISSN/ISSBN: 1932-6157
• DOI: 10.1214/13-AOAS665
• 发表日期: 2013
• 页码: 2062-2080
• 关键词: estimating medical costs; bladder-cancer; bias formulas; regression; care; survival; patterns; outcomes

摘要

Estimates of the effects of treatment on cost from observational studies are subject to bias if there are unmeasured confounders. It is therefore advisable in practice to assess the potential magnitude of such biases. We derive a general adjustment formula for loglinear models of mean cost and explore special cases under plausible assumptions about the distribution of the unmeasured confounder. We assess the performance of the adjustment by simulation, in particular, examining robustness to a key assumption of conditional independence between the unmeasured and measured covariates given the treatment indicator. We apply our method to SEER-Medicare cost data for a stage II/III muscle-invasive bladder cancer cohort. We evaluate the costs for radical cystectomy vs. combined radiation/chemotherapy, and find that the significance of the treatment effect is sensitive to plausible unmeasured Bernoulli, Poisson and Gamma confounders.