title: The use of propensity scores and observational data to estimate randomized controlled trial generalizability bias.
abstract: 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.
authors.affiliation: Quantum Health, Columbus, OH 43235, U.S.A.
authors.forename: Taylor R
authors.initials: TR
authors.lastname: Pressler
authors.forename: Eloise E
authors.initials: EE
authors.lastname: Kaizar
mesh_terms: D015982:Bias; D003198:Computer Simulation; D015986:Confounding Factors, Epidemiologic; D003627:Data Interpretation, Statistical; D005113:Extraction, Obstetrical / Q000295:instrumentation; D005260:Female; D006801:Humans; D015233:Models, Statistical; D057216:Propensity Score; D016032:Randomized Controlled Trials as Topic / Q000379:methods*; D016896:Treatment Outcome
keywords: causal effect; observational studies; propensity score; randomized controlled trials; sample selection error
references.citation: Am J Psychiatry. 2000 Apr;157(4):588-94
references.pmid: 10739418
references.citation: JAMA. 2002 Jun 5;287(21):2765-7
references.pmid: 12038906
references.citation: Stat Med. 1998 Oct 15;17(19):2265-81
references.pmid: 9802183
references.citation: J Nerv Ment Dis. 2004 Feb;192(2):87-94
references.pmid: 14770052
references.citation: Stat Sci. 2007;22(4):569-573
references.pmid: 18516239
references.citation: Am J Respir Crit Care Med. 2003 Dec 1;168(11):1308-11
references.pmid: 12893649
references.citation: J Consult Clin Psychol. 2003 Dec;71(6):963-72
references.pmid: 14622071
references.citation: Stat Med. 2011 Nov 10;30(25):2986-3009
references.pmid: 21898521
references.citation: Stat Med. 2008 May 20;27(11):1801-13
references.pmid: 18381709
references.citation: Multivariate Behav Res. 2011 May;46(3):399-424
references.pmid: 21818162
references.citation: Am J Epidemiol. 2011 Aug 1;174(3):345-53
references.pmid: 21659349
references.citation: Ann Fam Med. 2006 Mar-Apr;4(2):104-8
references.pmid: 16569712
references.citation: Obstet Gynecol. 1991 Nov;78(5 Pt 1):789-94
references.pmid: 1923198
references.citation: Stat Med. 2004 Oct 15;23(19):2937-60
references.pmid: 15351954
references.citation: J Clin Epidemiol. 1997 Jul;50(7):823-8
references.pmid: 9253394
references.citation: Thorax. 2007 Mar;62(3):219-23
references.pmid: 17105779
references.citation: Lancet. 2005 Jan 1-7;365(9453):82-93
references.pmid: 15639683