Scott Richardson and Piersante Sestini asked:
> 6. Should foreground questions about diagnostic tests always include a
> specification of pretest probability in the 'P' segment? An example: "in
> patients with leg swelling and low to intermediate probability of DVT ..."
As it happens, I sometimes do this if I my clinical decision is in such a specific patient group. But should EVERY diagnostic question do this, as one of the notes I received suggested? Don't know - what do others think?
This is a good point.
This is similar to have the severity of disease in the "P" for a
therapeutic question.
I usually don't, unless it is clear that the stage of disease may affect
the effectiveness of the test or treatment, so I expect that such
patients are addressed by separate studies. However, I admit that I
always keep it on my mind, to get over it later in the "application"
step: can I apply this evidence to my patient?
The problem that this has not happened even after 30+ years when it was originally proposed is that the question is useful only if ALL differential diagnostic, mutually exclusive, possibilities (which sometimes can be collapsed to 2 most important ones) are put forward. If one does not think about a particular diff. diagnosis then obviously postulating "P" will not be useful. For example, if in a patient with leg swelling I think of DVT, cellulitis, trauma, cardiac heart failure etc but forgot lymphedema then postulating "P" for DVT will not help me answer the question about post-test probabilities for lymphedema. We have all experienced those clinical situations where we were struggling to find out what is wrong with the patient and then a colleague comes along and points that the patient obviously had the disease "X" (while we all thought that he may have disease A, B, C etc but never thought of the disease "X"). The problem is that the problem-solving techniques are field-specific (someone can be a great cardiologist and a lousy oncologist and vice versa) and increases with knowledge. At the same time, as echoed frequently in the exchanges of the members of this group, the experts are also prone to their biases. We simply understand very little why we sometimes think about one diff. diagnosis only not to invoke it on the other occasion (and why we are right on some occasions and wrong on the others). Perhaps one day high-speed computers will be available at the bedside to calculate ALL known diff. diagnostic possibilities in real time (akin to "Big Blue" chess-playing computer), but in the mean time we need to strive to play like Kasparov.
ben
Benjamin Djulbegovic, MD,PhD
Professor of Oncology and Medicine
H. Lee Moffitt Cancer Center & Research Institute
at the University of South Florida
Department of Interdisciplinary Oncology
SRB #4, Floor 4, Rm #24031 (Rm# West 31)
12902 Magnolia Drive
Tampa, FL 33612
Editor: Cancer Treatment Reviews (Evidence-based Oncology Section)
http://www.harcourt-international.com/journals/ctrv/
e-mail:[log in to unmask]
http://www.hsc.usf.edu/~bdjulbeg/
phone:(813)979-7202
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