title: Randomized clinical trials and observational studies: guidelines for assessing respective strengths and limitations.
abstract: The 2 primary types of studies that are used to test new drugs or procedures or compare competing drugs or types of procedures are randomized clinical trials (RCTs) and observational studies (OS). Although it would appear that RCTs always trump OS because they eliminate selection bias, there are many possible limitations to both types of studies, and these limitations must be carefully assessed when comparing the results of RCTs and OS. This state-of-the art review describes these limitations and discusses how to assess the validity of RCTs and OS that yield different conclusions regarding the relative merit of competing treatments/interventions.
authors.affiliation: SUNY University at Albany, School of Public Health, Rensselaer, New York 12144-3456, USA. elh03@health.state.ny.us
authors.forename: Edward L
authors.initials: EL
authors.lastname: Hannan
mesh_terms: D003627:Data Interpretation, Statistical; D019317:Evidence-Based Medicine; D019983:Guideline Adherence; D006801:Humans; D019370:Observation; D017410:Practice Guidelines as Topic; D016032:Randomized Controlled Trials as Topic / Q000592:standards* / Q000706:statistics & numerical data; D012042:Registries / Q000592:standards; D015203:Reproducibility of Results; D012107:Research Design / Q000592:standards*; D015983:Selection Bias; D016896:Treatment Outcome