Tuesday, March 18, 2014

An oral history of evidence based medicine

JAMA and BMJ have posted a series of video interviews and a panel discussion with some of the founders of evidence based medicine (EBM). This is a must see if you're interested in a better understanding of EBM and its origins.

I'll open my discussion of the series with a quote from one of the panelists, Kay Dickersin, Director of the Johns Hopkins Center for Clinical Trials: “It is curious, even shocking, that the adjective 'evidence based' is needed. The public must wonder on what basis medical decisions are made otherwise. Is it intuition? Magic?” When I first encountered the term a couple of decades ago I wondered the same thing. What else had I been basing my practice on all that time if not on evidence?

Two of the interviews are with David Sackett, widely known as one of EBM's main apologists. He talked about the beginnings of the movement and emphasized that it is not merely a collection and critical appraisal (a term the EBM founders coined) of evidence. Rather, it goes beyond that to encompass the judgment of the individual clinician and the preferences and values of the individual patient. Those two elements often get left out of the discussion. Because the individual patient is a key element of EBM, proponents of medicine done by central planning can never claim to advocate for evidence based medicine. Along the same lines Dr. Gordon Guyatt remarked that there is no clinical decision that doesn't have the individual patient's preferences and values attached to it. As a corollary, evidence alone cannot inform a clinical decision.

Originally the founders were going to name the new movement “scientific medicine” but the basic science people at the table cringed. “We are scientific,” they protested. Hence the name EBM was created. The irony is that while the founders intended to be scientific the movement over time has played out as unscientific in many ways as I and others have documented. (Recognition of these unscientific aspects of EBM has given birth to another movement, Science Based Medicine, or SBM).

A good deal of the discussion centered around the Cochrane Collaboration. Regarded as a centerpiece of EBM the Cochrane Collaboration has become a platform for some unsound ideas (see here).

One of the discussants, Drummond Rennie, recalls the rise to prominence of meta-analysis. The rediscovery of meta-analysis in the 1970s, according to Rennie, was one of the antecedents of EBM. Meta-analysis offered a cohesive and logical way to synthesize seemingly disparate research studies. Without meta-analysis one was left only to select among contradictory lines of evidence. In an exaggeration Rennie says rather than do that one might as well have thrown out all old research.

Dr. Brian Haynes was asked whether EBM was too much work for the busy clinician. When one considers the steps involved in searching, critical appraisal and application it does seem a daunting task. Certainly it would have been too time consuming before the era of computer searching. On line searching was available in the 1980s (you had to go to considerable trouble to set it up) but had not yet reached prime time even by the time EBM was announced to the world in 1992.

Haynes said that he and his colleagues were working from the beginning to make the process user friendly in everyday practice. They have been exploring ways to put best evidence into secondary sources, including even textbooks (some EBM purists decry the use of textbooks) so that doctors will not have to do primary literature searches and critical appraisal. Currently available secondary resources, said Haynes, may not be where they need to be yet but are improving.

As Guyatt pointed out the leaders realized early on that getting all clinicians to search and critically appraise the literature individually was an unattainable ideal. The best that could be done was to educate clinicians in the principles of EBM so they could then make more intelligent and effective use of secondary sources. Evidence derived from such sources has already been critically appraised and has been referred to as “pre-processed” evidence. Some EBM purists, taking a negative view of this approach, consider it an unfortunate compromise and have called it “evidence based capitulation.”

There was an irritating tone throughout the series: the implication that before the launch of the movement known as EBM medical practice was not based on evidence, or even science, at all. That is simply not true. As I said in my post marking the 20th anniversary of EBM the movement did not bring us anything fundamentally new. The idea that evidence is necessary goes back as far as the scientific revolution of the 17th century. Over 100 years ago the Flexner Report emphasized the need for evidence to prevail over dogma. Clinical trials, even comparative effectiveness research, go back to at least the 1960s. All EBM really did was to give us a more systematic and rigorous way to apply the best evidence to patient care.

There were huge gaps between evidence and practice before the launch of the movement but there still are. These gaps, which are somewhat inscrutable, will narrow over time but never completely close.

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