ESTIMATING ODDS RATIOS UNDER A CASE-BACKGROUND DESIGN WITH AN APPLICATION TO A STUDY OF SORAFENIB ACCESSIBILITY

In certain epidemiologic studies such as those involving stress disorders, sexual harassment, alcohol addiction or epidemiological criminology, exposure data are readily available from cases but not from controls because it is socially inconvenient or even unethical to determine who qualifies as a true control subject. Consequently, it is impractical or even infeasible to use a case-control design to establish the case-exposure association in such situations. To address this issue, we propose a case-background design where in addition to a sample of exposure information from cases, an independent sample of exposure information from the background population is taken, without knowing the case status of the sampled subjects. We develop a semiparametric method to estimate the odds ratio and show that the estimator is strongly consistent and asymptotically normally distributed. Simulation studies indicate that the estimators perform satisfactorily in finite samples and against violations of assumptions. The proposed method is applied to a Sorafenib accessibility study of patients with advanced hepatocellular carcinoma.