The lack of evidence for the benefits of EBM

Evidence‐based medicine (EBM) is defined as the conscientious and judicious use of current best evidence in conjunction with clinical expertise and patient values to guide health care decisions 1, 2.

3 should benefit the population, little ‘high quality’ (according to EBM standards) empirical evidence exists that it does. In this respect little has changed since the ‘Users Guide to Evidence‐Based Medicine’ was first published in 1992: Our advocating EBM in the absence of definitive evidence of its superiority in improving patient outcomes may appear to be an internal contradiction … When definitive evidence is not available, one must fall back on weaker evidence … and on biologic rationale. The rationale in this case is that physicians who are up‐to‐date as a function of their ability to read the current literature critically, and are able to distinguish strong from weaker evidence are likely to be more judicious in the therapy they recommend … [and] make more accurate diagnoses 4. The question of what might constitute ‘best evidence’ is addressed in levels of evidence tables such as the one produced by the Oxford Centre for Evidence‐Based Medicine. Like most other evidence‐ranking schemes, systematic reviews of randomized trials are placed at the apex of the evidence pyramid with mechanistic reasoning and ‘expert opinion’ ranked at the bottom. It seems ironical then that although there are good rationales for why EBMbenefit the population, little ‘high quality’ (according to EBM standards) empirical evidence exists that it. In this respect little has changed since the ‘Users Guide to Evidence‐Based Medicine’ was first published in 1992:

The authors went on to suggest that ‘until more definitive evidence is adduced’ the adoption of EBM should ‘appropriately be restricted’ to three groups: those found the rationale compelling, those who wished to test EBM in educational trials and those who found ‘the practice of medicine in the new paradigm is more exciting and fun’ 4. The first group was large, and by the early 2000s the EBM movement was widely described as a health care ‘revolution’ 5, 6, being hailed by Time Magazine in 2001 as one of the most influential contemporary ideas 7. EBM's subsequent rise to ascendency as the prevailing medical paradigm has been called ‘meteoric’ 8.

EBM has been shown to improve practice in specific areas. For example, stroke and myocardial infarction aftercare was improved in light of new evidence 9, 10, and some harmful practices have been reduced when trials revealed the risks outweighed benefits (e.g. postmenopausal hormone replacement therapy) 11, 12. These examples are promising but anecdotal. In another example, a study comparing EBM‐trained McMaster graduates to ‘traditionally’ trained peers found the former more knowledgeable about hypertension guidelines at least 5 years after graduation 13. However, this outcome is a dreaded surrogate end point. How can we know that better knowledge of guidelines translates to better patient outcomes? Or that the time needed for learning critical appraisal had not meant that an essential part of the syllabus had been forfeited. Maybe McMaster graduates excelled in treating hypertension, but kept missing paediatric meningitis.

If EBM were the revolutionary movement it was hailed as, we would expect more than benefits demonstrated in specific cases. We would expect population‐level health gains, such as those that occurred after the introduction of antibiotics, improved sanitation and smoking cessation 14. Unfortunately, there is little evidence that EBM has had such effects.

No randomized trial accurately addressing the population outcomes of EBM is likely to be forthcoming as the methodological challenges of sample size, contamination, blinding, follow‐up and outcome measures are hard to overcome.

The macrolevel evidence about hard health care outcomes we do have suggests that the cost of health care continues to rise 15, improvements are plateauing (e.g. http://www.mortality‐trends.org) and trust in medical professionals is decreasing 16. Given that EBM firmly favours an empirical approach over expert opinion and mechanistic rationale, it is ironic that its widespread acceptance has been based on expert opinion and mechanistic reasoning, rather than EBM ‘evidence’ that it actually works.