The Mythology of Evidence-Based Medicine

Medical training is awash in catch phrases and shibboleths. Some can be useful (“When you hear hoofbeats, think horses not zebras”); others, perhaps overly simplistic (“If it’s not in the chart, it didn’t happen”). A current divination clinging to medical consciousness is the concept of evidence-based medicine (EBM).

The phrase is invoked in holy proclamations, to settle arguments, and to dismiss dissent. “Care Pathways,” “Practice Guidelines,” and “Best Practices” suggest preferred treatment regimens as presented in scientific studies. Although contributors insist these algorithms are only guidelines, many become reified in academic centers, court rooms, and have even been referenced in healthcare legislation proposals. Although the EBM concept is intended to animate logical medical protocols and to avoid irrational misadventures, the tenacity of overzealous acolytes is disproportionate to the foundation upon which EBM is built.

EBM derives from published studies, primarily from academic centers. Protocols generally attempt to minimize confounding variables-usually employing a list of exclusion criteria rivaling biblical begats. Though useful for statistical purposes, these studies often eliminate more complicated patients-those with challenging comorbidities who are more typically seen in the clinician’s office. Measured clinical improvement on the researcher’s rating scale may not mimic response seen outside the institution.

Panels designed to produce recommended treatment approaches for disorders require years to finalize a published document. Scientific articles proposed to major journals may not be published for a year or more after initial submission (Pick up any journal and observe the lapses between “received…” “revision received…” and “accepted…”). Following the arrival of DSM-V, studies will reference the previous DSM-IV criteria for years afterward (as has occurred after each preceding DSM iteration was released). By necessity, citations in major publications are dated. Thus, by its own standards, EBM derives from old evidence.

Although dated EBM may be a useful starting point, it does not deserve the reverence with which it is sustained. Scientific knowledge is transforming at an accelerated pace. What was understood about subjects-from omega-3 fatty acids to the serotonin transporter gene-has changed in relatively short time spans. Published guidelines cannot keep up with constantly changing information.

More dangerous is the threat of EBM being used further to control medical practice. Insurance companies often refer to broad, frequently outdated recommendations to disallow appropriate treatments. Some federal health care proposals recommend “expert panels” to develop standardized therapy protocols. Like insurance companies, such guidelines will undoubtedly demand less expensive approaches. Just as one antibiotic cannot treat every patient’s infection, so one antipsychotic cannot treat every patient’s psychosis.

However, psychiatry’s current inability to isolate and culture the “depressococcus bacterium” or the “SchizoH1N2 virus” has left the specialty vulnerable to demands for one-[cheap]-size-fits-all therapy. EBM confirms that, in the aggregate, old medicines are just as effective as newer ones and that generic drugs are just as effective as proprietary medications. EBM recommendations may apply to the average patient, but most physicians strive for treatment that is above average. For the individual patient in the examining room, the art of medicine may require an individualized approach, distinct from the dictates of EBM.

EBM infers old evidence. We must guard against the risk that it will also signify cheap and mediocre medicine.