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Evidence based medicine

What is evidence based medicine?

Evidence based medicine is the integration of individual clinical expertise with the best available scientific evidence.

Prof David Sackett and colleagues stated it well in an editorial in the British Medical Journal in 1996[1]:

Evidence based medicine is the conscientious, explicit, and judicious use of current best evidence in making decisions about the care of individual patients.  The practice of evidence based medicine means integrating individual clinical expertise with the best available external clinical evidence from systematic research.  By individual clinical expertise we mean the proficiency and judgment that individual clinicians acquire through clinical experience and clinical practice…  By best available external clinical evidence we mean clinically relevant research, often from the basic sciences of medicine, but especially from patient centred clinical research into the accuracy and precision of diagnostic tests (including the clinical examination), the power of prognostic markers, and the efficacy and safety of therapeutic, rehabilitative, and preventive regimens.  External clinical evidence both invalidates previously accepted diagnostic tests and treatments and replaces them with new ones that are more powerful, more accurate, more efficacious, and safer.

The scientific method has been the most successful tool developed to accurately expand the realm of empiric knowledge.  Many elements of health care are fundamentally questions that can be addressed by scientific inquiry, e.g., “is treatment A more effective than treatment B?”  In the presence of new, or expanded or better evidence, consideration should be given on whether a change in clinical practice is necessary.

Apparent conflict between clinical expertise and new clinical evidence can occur, typically when the conclusion of a newly published paper is contrary to established current practice.  Resolution of this conflict requires proficiency in the critical analysis of evidence; is the evidence and conclusion valid?  If so, even firmly held clinical beliefs should be swayed by better evidence.  We do not give our patients justice by holding dogmatic therapeutic beliefs.

What evidence based medicine is not

Evidence based medicine is not algorithmic or “cookbook” medicine.  It is about using the best evidence to inform clinical judgement for the individual patient.  It is sometimes criticised that evidence based medicine reduces the variation in clinical practice and debases individualised care.  However, if this is the result of abandoning poorer forms of evidence (such as incorrect beliefs, outdated beliefs, cognitive biases) as the foundation for clinical decisions, then the criticism is not valid.  The art of individualising patient care does not and should not preclude the use of best evidence.  Moreover, the art of medicine should not involve making rationally poor clinical decisions.

Evidence based medicine is not “ivory tower” medicine from “armchair clinicians”.  It is curious that the branch of medicine that has the greatest number of practitioners and number of health contacts with patients, where the delivery of evidence based medicine would have the greatest yield on patient outcomes, has also the most poorly developed research culture.  Research findings are sometimes met with disdain in feedback sections of general practitioner news publications and at times there is an open anti-intellectual hostility towards academics.   One needs not be a researcher to practice evidence based medicine.  Rather, a rational frame of mind in evaluating the basis of personal clinical decisions is what is needed.

Evidence based medicine is not a plot or device to restrict general practitioner autonomy. Biomedical ethics is what guides clinical practice and patient autonomy is one of its pillars [2].  For patients to best exercise their autonomy, objective understanding of their health options is required.  Clinicians fulfil their role in turn by being informed of the best available evidence.

Click here to read an excellent commentary by Straus and McAlister on the common criticisms of evidence based medicine [3].


[One unerring mark of love of truth]; the not entertaining any proposition with greater assurance than the proofs it is built upon will warrant.

An Essay Concerning Human Understanding, Chapter 19 (1690). John Locke, British philosopher and physician.


  1. Sackett DL, Rosenberg WM, Gray JA, et al.  Evidence based medicine: what it is and what it isn’t [editorial].  BMJ 1996;312:71
  2. Beauchamp TL, Childress JF. Principles of Biomedical ethics. New York 1994, 4th edition.
  3. Straus SE, McAlister FA. Evidence-based medicine: a commentary on common criticisms [commentary]. CMAJ 2000; 163 (7)
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