Regular readers know that I consider making the proper diagnosis the epitome of internal medicine (as well as many other specialties.) We know that we often miss diagnoses, but we often do not know why. I have often recommended Jerome Groopman’s book - How Doctors’ Think - as a primer on medical cognition. Currently he has a regular column in the ACP Internist. The current article gives a classic example of medical diagnostic error - Beware of ‘search satisfaction,’ a common cognitive error .
Dr. Ginsberg told us that he viewed this case as “a horse masquerading as a zebra.” Why didn’t we see the horse? To help answer the question, Dr. Ginsberg sent us this picture of how the mind may not perceive a visual abnormality.
If you see nothing wrong, try again. It took us several tries.
The current American Journal of Medicine has an interesting article on diagnostic error - Overconfidence as a Cause of Diagnostic Error in Medicine. This article is long and detailed. I recommend it only for those who want to study this problem in depth.
Tradeoffs in Time, Cost, and Accuracy
As clinicians improve their diagnostic competency from beginning level skills to expert status, reliability and accuracy improve with decreased cost and effort. However, using the strategies discussed earlier to move nonexperts into the realm of experts will involve some expense. In any given case, we can improve diagnostic accuracy but with increased cost, time, or effort.
Several of the interventions entail direct costs. For instance, expenditures may be in the form of payment for consultation or purchasing diagnostic decision-support systems. Less tangible costs relate to clinician time. Attending training programs involves time, effort, and money. Even strategies that do not have direct expenses may still be costly in terms of physician time. Most medical decision making takes place in the “adaptive subconscious.” The application of expert knowledge, pattern and script recognition, and heuristic synthesis takes place essentially instantaneously for the vast majority of medical problems. The process is effortless. If we now ask physicians to reflect on how they arrived at a diagnosis, the extra time and effort required may be just enough to discourage this undertaking.
Applying conscious review of subconscious processing hopefully uncovers at least some of the hidden biases that affect subconscious decisions. The hope is that these events outnumber the new errors that may evolve as we second-guess ourselves. However, it is not clear that conscious articulation of the reasoning process is an accurate picture of what really occurs in expert decision making. As discussed above, even reviewing the suggestions from a decision-support system (which would facilitate reflection) is perceived as taking too long, even though the information is viewed as useful.173 Although these arguments may not be persuasive to the individual patient,2 it is clear that the time involved is a barrier to physician use of decision aids. Thus, in deciding to use methods to increase reflection, decisions must be made as to: (1) whether the marginal improvements in accuracy are worth the time and effort and, given the extra time involved, (2) how to ensure that clinicians will routinely make the effort.
How important is diagnostic accuracy? I would argue that if we could measure accuracy we would have the best single measure of physician quality. However, we are forever challenged with developing a measure, because we have difficulty knowing the correct answer - that in fact is the problem.
Clearly, we should encourage physicians to take the time to think about diagnosis. Perhaps, we could actually help patients through the act of spending money on cognition. Perhaps, but then who would pay for me to think?

