title: External validity of randomised controlled trials: "to whom do the results of this trial apply?".
abstract: In making treatment decisions, doctors and patients must take into account relevant randomised controlled trials (RCTs) and systematic reviews. Relevance depends on external validity (or generalisability)--ie, whether the results can be reasonably applied to a definable group of patients in a particular clinical setting in routine practice. There is concern among clinicians that external validity is often poor, particularly for some pharmaceutical industry trials, a perception that has led to underuse of treatments that are effective. Yet researchers, funding agencies, ethics committees, the pharmaceutical industry, medical journals, and governmental regulators alike all neglect external validity, leaving clinicians to make judgments. However, reporting of the determinants of external validity in trial publications and systematic reviews is usually inadequate. This review discusses those determinants, presents a checklist for clinicians, and makes recommendations for greater consideration of external validity in the design and reporting of RCTs.
authors.affiliation: Stroke Prevention Research Unit, University Department of Clinical Neurology, Radcliffe Infirmary, Oxford OX2 6HE, UK. peter.rothwell@clneuro.ox.ac.uk
authors.forename: Peter M
authors.initials: PM
authors.lastname: Rothwell
mesh_terms: D003627:Data Interpretation, Statistical; D003657:Decision Making; D019317:Evidence-Based Medicine; D006801:Humans; D017063:Outcome Assessment, Health Care; D018579:Patient Selection; D017410:Practice Guidelines as Topic; D011643:Publishing; D016032:Randomized Controlled Trials as Topic / Q000592:standards; D015203:Reproducibility of Results; D012196:Review Literature as Topic; D016896:Treatment Outcome