The danger of assumptions in medicine


Category : Medical Rants

Early in my academic career I became fascinated with decision analysis.  I still like decision analysis as a strategy to make explicit the structure of a problem.  However, over time the major weakness of decision analysis became very clear.  The problem derives from the assumptions.

As usual, I will use pharyngitis to frame the problem.  Most articles and all the guidelines make the assumption that we can dichotomize pharyngitis into group A strep pharyngitis or "viral".  The problem here is that the assumption is wrong.

The assumption states implicitly that only group A strep pharyngitis requires antibiotic therapy.  This assumption might work for pre-adolescents, but in adolescents and young adults group C deserves treatment and as I write repeatedly, fusobacterium pharyngitis deserves treatment.

The assumption really explains the difference between the 2 US guidelines.  It explains many attempts to decrease antibiotic use by only treating rapid test positive sore throat patients.  

The authors of these papers also make the assumption that the rapid test is highly accurate.  That assumption may not work either.  Recent data, cited in this blog, call the quoted sensitivity of 90% or greater into question.

When caring for patients, we must always question our own assumptions and the assumptions of other physicians.  We owe our patients great skepticism.  When we take implicit assumptions and make them explicit, we are more likely to challenge the assumptions and adjust our thinking about the patient (or the clinical condition).

Euclid taught me that without assumptions there is no proof. Therefore, in any argument, examine the assumptions. – E. T. Bell

Comments (2)

Your last few lines are a gem; I made an assumption today on a patient case while choosing treatment over an open lung biopsy but carefully and explicitly told the patient that we are treating him with an assumption and if this line of treatment does not work, then we will go back to plan B. So timely to read this post.

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