Evidence-based medicine (EBM) puts forward a hierarchy of evidence for informing therapeutic decisions. An unambiguous interpretation of how to apply EBM's hierarchy has not been provided in the clinical literature. However, as much as an interpretation is provided proponents suggest a categorical interpretation. The categorical interpretation holds that all the results of randomised trials always trump evidence from lower down the hierarchy when it comes to informing therapeutic decisions. Most of the critical replies to EBM react to this interpretation. While (...) proponents of EBM can avoid some of the problems raised by critics by suitably limited the claims made on behalf of the hierarchy, further problems arise. If EBM is to inform therapeutic decisions then a considerably more restricted, and context dependent interpretation of EBM's hierarchy is needed. (shrink)

In this essay, we defend the design of the Salk polio vaccine trial and try to put some limits on the role schemata should play in designing clinical research studies. Our presentation is structured as a response to de Freitas and Pietrobon who identified the CONSORT statement as a schema that would have, had it existed at the time, ruled out the design of the Salk polio vaccine trial of 1954 in favor of a completely randomized controlled clinical trial. We (...) argue that large-scale public health interventions often require evidence beyond simple efficacy, the limit of what an RCT can provide, and that the design actually adopted for the Salk trial represented a reasonable—albeit imperfect—compromise. This is of more than historical interest in that many contemporary studies are of the scale and scope to require a more pragmatic, rather than explanatory, approach to study design. (shrink)