Evidence based medicine – misinterpreted and not sufficient


Category : Medical Rants

I am a huge fan of evidence. Many treatment paradigms have changed during my career because evidence showed that common wisdom was wrong.  I have two issues with the term EBM.

The first problem is a misinterpretation of EBM.  Evidence is not absolute; it requires context.  One study rarely should have a major impact on our strategies.  We need an accumulation of evidence unless the study has dramatic findings.

We must be careful to avoid applying evidence without a full understanding of the context of the studies.  We should not overestimate epidemiologic data.

So that is the first step.  Let me give an example.  We know from epidemiologic data that lower HgbA1c in diabetes correlates with less complications.  Diabetologists therefore have argued for lowering the goal HgbA1c.  Recent data suggest that a lower goal may lead to more complications in more complex patients.  This general principle of applying evidence taken from single disease studies to multiple disease patients is known to EBM afficionados, but too often forgotten by single disease experts.

The second problem comes from not knowing the underlying physiology.  We do not have strong evidence for every issue in medicine.  I cannot point to randomized controlled trials of diuretic therapy in CHF, but by knowing the physiology I can hopefully use diuretics intelligently.

EBM does not deny the value of physiology, but too often EBM receives misinterpretation.  If we do not understand the pathophysiology we can make mistakes in EBM interpretation.

Too many "experts" teach to the disease rather than the patient.  Let me use pharyngitis as an example.  We know that most pharyngitis is self-limited.  Some argue that we do not even need to treat group A strep pharyngitis.  Most experts recommend a rapid test – treat if positive and avoid antibiotics if negative.  Generally that is true.  But a lack of understanding the physiology of the infection allows physicians to make the mistake of seeing sore throats as a simple disease.  Thus physicians sometimes ignore the patient's signs and symptoms because of the anchoring of the sore throat symptom. 

We must learn evidence and apply evidence wisely.  EBM should not ever become prescriptive, rather it provides one more input into physician decision making.

The suits and bean counters can hardly imagine this problem.  They look at treatment issues as purely a left brain function.  We must use our whole brain to better understand whether or not the patient fits the algorithm.  Great physicians understand this.  We who teach have an obligation to try to teach this attitude.  Thus, we cannot just rely on teaching evidence.  We should not just teach what to do, but rather we should make explicit why we should take an action.

We must allow for the exceptions and be able to explain them.  I may be biased, but too often I see this as a lost art.

Comments (5)

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My word of caution regarding physiology, however, would be to never assume that understanding the physiology will lead to correct treatment.  Instead, physiology should be the starting point for studies.  The over-used but true example is that giving inotropes in CHF makes a lot of sense given the physiology.  Giving beta-blockers seems foolhardy.  In retrospect, beta-blockade does make sense, but it was only through the push for evidence-based practice that we discovered that.

That said, your point is well taken that no study applies to all patients, and only by understanding physiology can we accurately apply evidence to the patient in front of us.

I am a huge fan of evidence based medicine as it is science and makes sense.  In a recent argument with my sister, the economics grad student I was reminded of the reality of of publication bias, reminding me that even evidence can be flawed.

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