Threats to applicability of randomised trials : exclusions and selective participation.
Although the randomised controlled trial (RCT) is regarded as the « gold standard » in terms of evaluating the effectiveness of interventions, it is susceptible to challenges to its external validity if those participating are unrespresentative of the reference population for whom the intervention in question is intended.
In the past, reporting on numbers and types of potential subjects that have been excluded by design, and centres, clinicans or patients that have elected not to participate, has generally been poor, and the threat to inference posed by possible selection bias is unclear.
A systematic review was undertaken, based largely on MEDLINE and EMBASE with follow-up of cited references, to assess the extent, nature and importance of excluding potential subjects or the unwillingness of particular centres, clinicians or patients to participate.
RCTs vary widely in the extent to which potential future recipients of treatment are included.
The reasons cited for excluding certain categories of patient may be medical or scientific.
Medical reasons included a high risk of adverse effects and the belief that benefit will be relatively small or absent (or has already been established) in the groups in question.
Scientific reasons include more precise estimates of treatment effect because of a relatively homogeneous sample and the reduction of potential bias by excluding those individuals most likely to be lost to follow-up. (...)
Mots-clés Pascal : Essai clinique, Validité, Bibliographie, Biais méthodologique, Epidémiologie, Méthode étude, Pronostic, Médecin, Pratique professionnelle, Effet secondaire
Mots-clés Pascal anglais : Clinical trial, Validity, Bibliography, Methodological bias, Epidemiology, Investigation method, Prognosis, Physician, Professional practice, Secondary effect
Notice produite par :
ORS Auvergne - Observatoire Régional de la Santé d'Auvergne
Code Inist : 002B30A11. Création : 06/10/1999.