Reviving Cochrane's contribution to evidence-based medicine: bridging the gap between evidence of efficacy and evidence of effectiveness and cost-effectiveness.

Throughout the quarter century since the advent of evidence-based medicine (EBM), medical research has prioritized 'efficacy' (i.e. internal validity) using randomized controlled trials. EBM has consistently neglected 'effectiveness' and 'cost-effectiveness', identified in the pioneering work of Archie Cochrane as essential for establishing the external (i.e. clinical) validity of health care interventions. Neither Cochrane nor other early pioneers appear to have foreseen the extent to which EBM would be appropriated by the pharmaceutical and medical devices industries, which are responsible for extensive biases in clinical research due to selective reporting, exaggeration of benefits, minimization of risks, and misrepresentation of data. The promise of EBM to effect transformational change in health care will remain unfulfilled until (i) studies of effectiveness and cost-effectiveness are pursued with some of the same fervour that previously succeeded in elevating the status of the randomized controlled trial, and (ii) ways are found to defeat threats to scientific integrity posed by commercial conflicts of interest.