Evidence-based medicine: what is the evidence that it has made a difference?

Evidence-based medicine (EBM) has, over the past 20 years, made us all more critical in our thinking about the efficacy and safety of interventions. This is evident in the higher standards of our spoken and written work, formal and informal, and in our approach to the subject. The downside has been the coincidence of the squeeze on healthcare funding with the emergence of the EBM ideas - it has been all too easy to misuse the tools of EBM to deny patients access to treatment, and this, together with the off-putting political correctness of the EBM approach in some quarters, has made clinicians uneasy. Clinicians have to make decisions about therapy for the individual patient. Ideally this is guided by the best available evidence and their experience. EBM can guide one as to the population efficacy and safety of a particular intervention, but as we all know few patients are average. That guidance can only be given if there is adequate evidence, and the difficulty with guidance about symptom control is often the paucity of evidence of sufficient quality to yield credible guidance. Palliative care is often a 'complex intervention', and here EBM struggles to untangle which components, if any, of the complex interventions are important. The trial and review methodologies for complex intervention are wanting. Tom Chalmers, a grandfather of the EBM movement, argued late in his career that the most important function of the EBM approach was to frame the research agenda. This we think is correct. The process of systematic review of a topic throws up the deficits in trial methods and the lacunae in the data, and this then can show the way forward.