William Cayley: Evidence based medicine—it’s time to be critical

bill_cayley“If it ain’t broke, don’t fix it” goes the aphorism—and so would say any who trust complacently in the exponential growth of “evidence based” this or that in medicine. Des Spence, for one, disagrees. In a recent BMJ editorial he argues evidence based medicine (EBM) is broken, it is “now the problem, fuelling overdiagnosis and overtreatment.”

To the extent that one thinks of “EBM” as a consensus among medical and healthcare professionals that involves giving evidence ratings to every pronouncement, and adding the moniker “evidence based” to every product or guideline, I would agree. From the early discussions of taking an evidence based approach to critical appraisal that was advocated by Guyatt and Sackett in the 1990s, the “evidence based medicine” approach has evolved from an adjective describing critical thinking, to a near Leviathan of consensus that seems to buy into anything labelled “evidence based.” We have moved from worshipping what “the experts” say, to giving near universal acceptance to anything that comes with the statement “there is evidence that…”

However, if evidence based medicine (I mean this here as an adjective describing an approach to medical care, not the acronym “EBM” that is now nearly universal) is really about critical thinking, then, I would argue, it is far from dead or broken. Recent years have seen the development of the Preventing Overdiagnosis movement, and the work behind a Cochrane review on oseltamivir has been in part responsible for a push for more openness of pharmaceutical company data. These and other initiatives (which Des Spence acknowledges) have arisen out of the critical thinking that true evidence based medicine, focusing on the outcomes that truly matter to patients (ie, helping them live longer or better), aims to foster.

There will always be a tendency for any innovation or new approach to be co-opted (intentionally or not) into something else. But if we seek to keep to the ideals of evidence based medicine, critically evaluating and applying the best information to care for our patients, then we will do well in the long run. It takes effort to go beyond what the guidelines, experts, and adverts give us, but that work is part of medicine—and critical thinking about how to do a better job of curing, comforting, and caring is at the heart of being a doctor.

Competing interests: “I declare that I have read and understood the BMJ Group policy on declaration of interests and I have no relevant interests to declare beyond a passion for clear and critical thinking..”

William E Cayley Jr practises at the Augusta Family Medicine Clinic, teaches at the Eau Claire Family Medicine Residency, and is a professor at the University of Wisconsin, Department of Family Medicine.

  • David_Colquhoun

    Quite right.

    The problem is that the description “evidence-based” has become universal, even when the evidence is lousy.

    What is cause for optimism is the rise of the critical thinking movement. It started in pub basements with the Skeptics in the Pub meetings. And it has been in the lead in weeding out overblown claims, whether they come from alternative medicine or Big Pharma,

    If you want critical thinking don’t turn to regulatory agencies which have proved to be toothless. Look (selectively) at blogs.

  • Will Wiegman

    I think ‘evidence based medicine’ should take a cue from recent discoveries by the DNA analysis group that most diseases have more than one related cause, usually by bacteria colonies living discreetly within protected areas of the body and hibernating in different forms until conditions are ripe for them to resume activity.

    We need to simply take advantage of increasingly cheaper new methods of analysis to help discern the difference between a system based failure and one influenced by the presence of bacteria that are modifying the body’s systemic reaction in their favor thereby mimicking a seemingly unrelated disease that exists solely because of their presence.

    Finding and treating the cause of a systemic disease instead of modifying the symptoms back into the realm of normalcy needs to be the SOP in the future!

  • Jd LaBash

    Should we really be surprised that the latest swing of intellectual fashion towards empericism should prove a disappointment? Evidence-based medicine will continue to contribute to the progress of medicine. However, evidenced-based medicine will only be applicable to a small subset of medical questions because of inherent limitations. Finite resources and populations prevent “A” level recommendations from being available for the majority of conditions. The requirements for study reliability intrinsically run counter to the requirements for generalized applicability; constraints to eliminate bias are themselves a form of bias.

    The interpretation of conclusions from evidence-based studies is not as clear cut as we are led to believe. The mathematical models on which statistical calculations are based include assumptions that may be inappropriate to the study (most importantly, assuming a normal distribution.) Experience shows that peer review is not adequately addressing this problem. Practical utility is compromised by the disconnect between the specialized use of statistical terms and the clinicians’ meaning for the same terms (“significant” and “no evidence to suggest” are striking examples of this caveat.) “Statistics don’t lie”, but statistics don’t die either.

  • Jd LaBash

    I see a similar cautionary tale from the history of musical genres. As “Ragtime” , “Swing” and “Rock” became such dominant forms that an era took on their names, creations that only superficially qualified for inclusion began to dilute and degrade the genres until they were ripe for replacement by the “next big thing.”

    Similarly, music industry executives and music critics did little to resist this process. Nonetheless, some excellent works survive the test of time. The same will probably hold true for good evidence-based medicine. As for the remainder, i quote {Science Fiction writer Theodore} Surgeon’s Law: “90% of everything is crap.”

  • TheMedicalRoundtable

    Drs. Cayley and Colquhoun make powerful points, and while EBM has been morphed beyond what its label can support (I’m dropping in Ben Goldacre and AllTrials for the perspective that all evidence is skewed), clinical experience has an invaluable role in interpreting the data – even platinum level evidence that’s created for the ‘average” patient, needs to have the learned intermediary apply it to the suffering individual at bedside.

    We recently published a discussion between Drs. Guyatt and Tonnelli about the Role of Experience in an Evidence Based Practice which is open access. Dr. Tonelli made the point that opinion is not empirical and therefore should not be considered in the same silo as data when evaluating the statements/guidance.Dr. Guyatt discussed his ongoing work with the GRADE Working Group.


  • kakketoe

    Evidence based has become evidence biased