The use of propensity scores and observational data to estimate randomized controlled trial generalizability bias

• Published in: Statistics in medicine Vol. 32; no. 20; pp. 3552 - 3568
• Main Authors: Pressler, Taylor R., Kaizar, Eloise E.
• Format: Journal Article
• Language: English
• Published: England Blackwell Publishing Ltd 10.09.2013; Wiley Subscription Services, Inc
• Subjects: Bias; causal effect; Cause & effect diagrams; Clinical trials; Computer Simulation; Confounding Factors (Epidemiology); Data Interpretation, Statistical; Extraction, Obstetrical - instrumentation; Female; Humans; Medical errors; Medicine; Models, Statistical; observational studies; Propensity Score; randomized controlled trials; Randomized Controlled Trials as Topic - methods; sample selection error; Samples; Statistical methods; Treatment Outcome; sample selection error; causal effect; observational studies; randomized controlled trials; propensity score
• ISSN: 0277-6715; 1097-0258
• DOI: 10.1002/sim.5802

Although randomized controlled trials are considered the ‘gold standard’ for clinical studies, the use of exclusion criteria may impact the external validity of the results. It is unknown whether estimators of effect size are biased by excluding a portion of the target population from enrollment. We propose to use observational data to estimate the bias due to enrollment restrictions, which we term generalizability bias. In this paper, we introduce a class of estimators for the generalizability bias and use simulation to study its properties in the presence of non‐constant treatment effects. We find the surprising result that our estimators can be unbiased for the true generalizability bias even when all potentially confounding variables are not measured. In addition, our proposed doubly robust estimator performs well even for mis‐specified models. Copyright © 2013 John Wiley & Sons, Ltd.