Evidence based medicine and ethics.

Evidence based medicine is an important modern movement. It has its evangelists; it has its enemies; and now it has the journal: Evidence Based M-edicine. One can tell that a movement is important when its detractors heatedly maintain that it is nothing new. 'Evidence based medicine?' one chemist said to me, 'What other kind of medicine could there possibly be?' and a consultant physician said gruffly: 'We have always practised evidence based medicine'. My wife, who is a general practitioner, recently referred a fifty-year-old woman who was on hormone replacement therapy (HRT) for surgery. On the day of the operation, after she had been admitted, the woman was sent home by the anaesthetist because of the HRT. My wife believed that there was no good evidence that HRT increased the risks from surgery. She spoke to the anaesthetist and was told that it was 'received wisdom' that HRT increased morbidity. No further reasons were given or thought necessary. The hospital had no guidelines or policy on this issue. Evidence based medicine has developed as a critical response to just this kind of behaviour. It emphasises the point that it is not the authority of the doctor that justifies a particular clinical intervention, but the evidence for the intervention's effectiveness. Davidoff and colleagues (1) identify five linked ideas as central to evidence based medicine. They write: 'Firstly, clinical decisions should be based on the best available scientific evidence; secondly, the clinical problem rather than the habits of protocols should determine thetype of evidence to be sought; thirdly, identifying the best evidence means using epidemiological and biostatistical ways of thinking; fourthly, conclusions derived from identifying and critically appraising evidence are useful only if put into action in managing patients or making health care decisions; and, finally, performance should be constantly evaluated'. Evidence based medicine recognises a hierarchy in the quality of evidence, with systematic reviews of randomised controlled trials at the top of this hierarchy. Retrospective studies are well down the list and clinical anecdotes are seen as providing little if any evidence for the value of an intervention. Autonomous authorisation