Evidence based medicine: what it is and what it isn't

Sir William Osler once said “The practice of medicine is an art, based on science. Medicine is a science of uncertainty and an art of probability.

It’s about integrating individual clinical expertise and the best external evidence

As evidence based medicine continues to evolve and adapt, now is a useful time to refine the discussion of what it is and what it is not. 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. Increased expertise is reflected in many ways, but especially in more effective and efficient diagnosis and in the more thoughtful identification and compassionate use of individual patients’ predicaments, rights, and preferences in making clinical decisions about their care.

 By best available external clinical evidence, we mean clinically relevant research,  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. Good doctors use both individual clinical expertise and the best available external evidence, and neither alone is enough. Without clinical expertise, practice risks becoming tyrannised by evidence, for even excellent external evidence may be inapplicable to or inappropriate for an individual patient. Without current best evidence, practice risks becoming rapidly out of date, to the detriment of patients.

This description of what evidence based medicine is helps clarify what evidence based medicine is not. Studies show that busy clinicians who devote their scarce reading time to selective, efficient, patient driven searching, appraisal, and incorporation of the best available evidence can practice evidence based medicine.

External clinical evidence can inform, but can never replace, individual clinical expertise, and it is this expertise that decides whether the external evidence applies to the individual patient at all and, if so, how it should be integrated into a clinical decision. Similarly, any external guideline must be integrated with individual clinical expertise in deciding whether and how it matches the patient’s clinical state, predicament, and preferences, and thus whether it should be applied.


   1 .Promotes critical thinking

   2 .Requires clinicians to be open-minded

   3 .Encourages researchers to focus on evidence and outcomes that are important to clinicians and  patient

Doctors practising evidence based medicine will identify and apply the most efficacious interventions to maximise the quality and quantity of life for individual patients;

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