Basic Features of Evidence-based Medicine

Created on Sun, 04/16/2017 - 17:39
Last updated on Wed, 09/06/2017 - 21:39

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This chapter answers parts from Section A(a) of the old 2011 Primary Syllabus; "Describe the features of evidence-based medicine, including levels of evidence (eg. NH&MRC), meta-analysis and systematic review". It closely resembles the Fellowship exam revision chapter, "Definition and relevance of evidence based medicine". It must be pointed out that thought his topic occupies a position of prominence in the out of date primary curriculum (it literally is the first thing in there), at no stage were any primary candidates ever expected to describe the features of evidence-based medicine, or to debate the pros and cons of EBM as an approach to clinical medicine. Presumably, something like that would require the maturity and finesse expected of a candidate at the end-game. Indeed, the topic has come up several times in the Fellowship exam (Question 17 from the first paper of 2012 and to a lesser extent Question 2b from the first paper of 2001), where the candidates were expected to define "evidence-based medicine". Now that the statistics questions are migrating into the Fellowship exam, we can probably expect this area to be explored more frequently.

Definition of evidence-based medicine

The above-linked Required Reading chapter is more relevant to the Fellowship exam, and deals with this topic in greater detail (i.e. by outlining the advantages and disadvantages of EBM. In brief, EBM can be defined using a David Sackett quote used by the CICM examiners in the fellowship exam, as follows:

"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."

Insofar as the Primary exam goes, that sort of definition would probably be excessive. From past papers it is clear that the examiners have never been interested in it. However, the Primary syllabus does ask that the trainees be able to describe the features of evidence-based medicine.

What are those, then?

Features of evidence-based medicine

This is actually very difficult to describe, and even the original Sackett paper does little to render the term less ambiguous. Beverly Wood (1999) made an excellent attempt, which is remixed and offered below. In short, evidence-based medicine is a series of assumptions we make and a collection of rules we use to advise ourselves regarding clinical decisionmaking. 

The cardinal assumptions which make up the practice of evidence medicine are:

  • An understanding of pathophysiology or the reliance on authority and experience are alone insufficient as foundations for medical decisionmaking.
  • Clinicians should use base their decisionmaking on scientific data.
  • The data they use should ideally be from systematic reproduceable and unbiased studies. This increases the confidence in the effectiveness of therapies, accuracy of tests etc.
  • In order for this data to be used intelligently, the clinician must be able to analyse the quality of the evidence, using standardised tools.
  • Rather than replacing traditional methods (founded upon clinical experience and pathophysiology), evidence-based medicine is an evolution of these methods.

The process of using evidence medicine is:

  • Formulation of a specific question
  • Collection of suitable specific literature
  • Critical appraisal of that literature
  • Incoporation of the result with other reliable sources
  • Adjustment of the result according to personal clinical experience 
  • Development of rules or approaches which apply the findings of this process
  • Evaluation of the resulting outcomes

The alternative to evidence-based medicine is "eminence-based medicine", a pejorative term used to describe the reliance on authority and experience. This approach is actually not dead. People still learn from respected elders, and follow their lead even after they finish their training (and the increasingly dottery elder is bundled off to teach quietly at some university campus). This traditional approach to medicine is founded in pathophysiology, which was at one stage the only guiding light for practitioners. The assumption was that a sound understanding of the disease process would allow one to make scientific decisions as to how to reverse it. One critique of such an assumption is the extrapolation of frequently inaccurate physiological data. Such data was usually collected as an isolated experimental result, often from animals or even disembodied animal tissues. How, then, does one extrapolate the findings from an experiment on cultured rat fibroblasts to the complexity of a living human organism? This strategy gave us "normal" saline, among other horrible things. 



Sackett, David L., et al. "Evidence based medicine: what it is and what it isn't." (1996): 71-72.

Brown, Gary C., Melissa M. Brown, and Sanjay Sharma. "Value-based medicine: evidence-based medicine and beyond.Ocular immunology and inflammation 11.3 (2003): 157-170.

Wood, Beverly P. "What's the Evidence? 1." Radiology 213.3 (1999): 635-637.