title: Doubly-robust estimators of treatment-specific survival distributions in observational studies with stratified sampling.
abstract: Observational studies are frequently conducted to compare the effects of two treatments on survival. For such studies we must be concerned about confounding; that is, there are covariates that affect both the treatment assignment and the survival distribution. With confounding the usual treatment-specific Kaplan-Meier estimator might be a biased estimator of the underlying treatment-specific survival distribution. This article has two aims. In the first aim we use semiparametric theory to derive a doubly robust estimator of the treatment-specific survival distribution in cases where it is believed that all the potential confounders are captured. In cases where not all potential confounders have been captured one may conduct a substudy using a stratified sampling scheme to capture additional covariates that may account for confounding. The second aim is to derive a doubly-robust estimator for the treatment-specific survival distributions and its variance estimator with such a stratified sampling scheme. Simulation studies are conducted to show consistency and double robustness. These estimators are then applied to the data from the ASCERT study that motivated this research.
authors.affiliation: Department of Statistics, North Carolina State University, Raleigh, North Carolina 27695, U.S.A.. xbai3@ncsu.edu.
authors.forename: Xiaofei
authors.initials: X
authors.lastname: Bai
authors.forename: Anastasios A
authors.initials: AA
authors.lastname: Tsiatis
authors.forename: Sean M
authors.initials: SM
authors.lastname: O'Brien
mesh_terms: D003324:Coronary Artery Disease / Q000401:mortality* / Q000601:surgery*; D003627:Data Interpretation, Statistical; D006801:Humans; D064887:Observational Studies as Topic / Q000379:methods*; D017063:Outcome Assessment, Health Care / Q000379:methods*; D015995:Prevalence; D015203:Reproducibility of Results; D018401:Sample Size; D012680:Sensitivity and Specificity; D016008:Statistical Distributions; D016019:Survival Analysis; D016896:Treatment Outcome; D014481:United States / Q000453:epidemiology
keywords: Cox proportional hazard model; Double robustness; Observational study; Stratified sampling; Survival analysis