Intended for healthcare professionals


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

BMJ 1996; 312 doi: (Published 13 January 1996) Cite this as: BMJ 1996;312:71

What constitutes expert opinion?

The rapid response of Abt H Mat Sain importantly reminds us of the
dual pillars which David Sackett described as the foundation of Evidence
Based Medicine. While there may be some argument about what constitutes
the best external evidence, approaching this is infinitely easier than
clearly defining the second pillar on which the concept of Evidence Based
Medicine rests; what David Sackett called "individual clinical expertise".
He describes this as reflecting the proficiency and judgment that
physicians acquire through clinical practice.

There is a qualitative aspect to these attributes, but we have not
articulated criteria that might help us to decide who is to be relied
upon to provide the soundest expert clinical judgement. Because of this
(and some other factors), Evidence Based Medicine is in danger of becoming
the very thing it sought to avoid. That is to escape from recommendations
based on authority.

Today, all too often, those whose opinions are sought are experts by
virtue of their elevation to this rank by the marketing departments of
drug manufacturers. These might be the "key opinion leaders" or KOLs whose
expert opinions cannot be regraded as free from influence by evident
conflicts of interest. Promotional material from educational entities
funded by industry, often tell us that their recommendations are evidence
based. But it is not beyond conjecture that an expert has been created
expressly to justify such a claim.

We may have no way to assess the proficiency of the expert whose
opinion is sought. An association with an academic institution is really
not enough and a long list of publications may also be irrelevant, but the
number of years in clinical practice might be helpful. As long as what
constitutes individual clinical expertise remains unquestioned and poorly
defined, clinical recommendations may indeed be made by the kind of
authority that Evidence Based Medicine sought to avoid.

Experts on various clinical guidelines committees in the US declare
conflicts of interest, usually related to receiving payments from drug
manufacturers. They provide the clinical expertise, that together with a
consideration of external evidence justifies the claim that the
recommendations they help to formulate are evidence based. We are far from
assured that these individuals necessarily have the requisite clinical
experience to provide the clinical judgment that David Sackett stated was
necessary to be intergrated with the best external evidence.

In this way, there is a danger that the current application of
Evidence Based Medicine may succeed in creating the very condtion it was
meant to avoid.

Competing interests:
None declared

Competing interests: No competing interests

31 October 2008
Joseph A Sonnabend
retired physician
London NW8 9UG