title: Causal inference with missing exposure information: Methods and applications to an obstetric study.
abstract: Causal inference in observational studies is frequently challenged by the occurrence of missing data, in addition to confounding. Motivated by the Consortium on Safe Labor, a large observational study of obstetric labor practice and birth outcomes, this article focuses on the problem of missing exposure information in a causal analysis of observational data. This problem can be approached from different angles (i.e. missing covariates and causal inference), and useful methods can be obtained by drawing upon the available techniques and insights in both areas. In this article, we describe and compare a collection of methods based on different modeling assumptions, under standard assumptions for missing data (i.e. missing-at-random and positivity) and for causal inference with complete data (i.e. no unmeasured confounding and another positivity assumption). These methods involve three models: one for treatment assignment, one for the dependence of outcome on treatment and covariates, and one for the missing data mechanism. In general, consistent estimation of causal quantities requires correct specification of at least two of the three models, although there may be some flexibility as to which two models need to be correct. Such flexibility is afforded by doubly robust estimators adapted from the missing covariates literature and the literature on causal inference with complete data, and by a newly developed triply robust estimator that is consistent if any two of the three models are correct. The methods are applied to the Consortium on Safe Labor data and compared in a simulation study mimicking the Consortium on Safe Labor.
authors: Division of Biostatistics, Office of Surveillance and Biometrics, Center for Devices and Radiological Health, Food and Drug Administration, Silver Spring, MD, USA zhiwei.zhang@fda.hhs.gov.
authors: Zhiwei
authors: Z
authors: Zhang
authors: Department of Mathematics, Harbin Institute of Technology, Harbin, P.R. China.
authors: Wei
authors: W
authors: Liu
authors: Biostatistics Core, School of Biological and Population Health Sciences, College of Public Health and Human Sciences, Oregon State University, Corvallis, OR, USA.
authors: Bo
authors: B
authors: Zhang
authors: Department of Biostatistics, St. Jude Children's Research Hospital, Memphis, TN, USA.
authors: Li
authors: L
authors: Tang
authors: MOE and Shanghai Key Laboratory of Children's Environmental Health, Xinhua Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, P.R. China.
authors: Jun
authors: J
authors: Zhang
mesh_terms: D003627:Data Interpretation, Statistical; D005260:Female; D006801:Humans; D007743:Labor, Obstetric; D064887:Observational Studies as Topic / Q000379:methods*; D011247:Pregnancy; D012107:Research Design; D016896:Treatment Outcome
keywords: counterfactual; double robustness; inverse probability weighting; missing at random; missing covariate; propensity score; triple robustness