[EXTERNAL][IMPROVEDX] Balancing misclassification costs & numerators\denominators

Shaneyfelt, Terry Terry.Shaneyfelt at VA.GOV
Wed Dec 18 16:10:30 UTC 2013


Wow...where to begin. All diagnosis, at some level, is based on probability. You might do it subconsciously or use qualitative terms like "likely" or "probably has" but in your mind this is assigned a probability or range of probabilities. Even pattern recognition if you think about it has probability associated with it- probably greater than 90-95% (maybe higher).

Not all ST elevation is an acute MI. Pericarditis, amongst other things, can do this. So even in the case you reference there is probability that this is acute MI (going to be low in the 20 yr old), pericarditis (going to be much higher in the 20 yr old), etc. 

Using and interpreting testing properly is probability based. A very low risk person with chest pain should not undergo cardiac testing. The test is unlikely to move us over a treatment threshold.  A very high risk person doesn’t need it either (a negative test isn’t going to move use below the testing threshold) Testing is only useful in intermediate probabilities. Again that word...probability. 

Clinical prediction rules can estimate probabilities in individual patients as a starting point for evaluation. 


-----Original Message-----
From: Bimal Jain [mailto:bjain at PARTNERS.ORG] 
Sent: Wednesday, December 18, 2013 8:07 AM
To: IMPROVEDX at LIST.IMPROVEDIAGNOSIS.ORG
Subject: Re: [IMPROVEDX] [EXTERNAL][IMPROVEDX] Balancing misclassification costs & numerators\denominators

I find the discussion about role of probabilities in diagnosis, for example, of acute cardiac ischemia fascinating. I believe, probabilities have little or no role in clinical diagnosis, as our goal is to diagnose a disease correctly in a particular, individual patient. In such a patient, a probability, whether high or low is not evidence for presence or absence of disease. A probability only informs us about distribution of disease in a series of patients but tells us nothing about disease in a particular patient. A clinical presentation should be employed, I suggest, only to suspect a disease, regardless of whether the prior probability is low or high. The suspected disease should then be evaluated by tests which yield highly informative results. For example, acute Q wave and ST elevation changes in EkG alone should lead to definitive diagnosis of acute myocardial infarction, regardless of whether its prior probability is high or low. I believe, basing clinical diagnosis on probabilities is a major source of diagnostic error which can be avoided by recognising their non-role in diagnosis.

Bimal P Jain, MD
Pulmonary-Critical Care
North Shore Medical Center (Union)
Lynn, MA 01904

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