Sunday, March 25, 2007

How doctors think and the importance of "check your premises"

Jerome Groopman's new book, "How Doctors Think" has attracted a bit of media attention replete with a favorable write-up in Time magazine.

Groopman discusses a topic of considerable personal interest and one that I have blogged about now and again. The topic of how cognitive mechanisms such as heuristics serve us well most of the time but can also lead us down a very wrong end is well is illustrated by Groopman with clinical histories, sometimes of his own medical adventures and misadventures. Placing the abstract concepts with real life clinical vignettes give them limbic valence.

Pattern recognition seems to be very important in the diagnostic acumen of experts and a well functioning pattern recognition system which develops over time and with experience seems to be a major distinguishing feature of the expert from the novice. It is useful but not perfect based as it is based on generalizations and abstractions. Generalizations are generally right but not always- so that even with optimal functioning of pattern recognition mistakes can occur.

This pattern recognition system ( a.k.a heuristics, or mental shortcuts) while serving the expert well comes with a dark side, one aspect of which is the phenomenon of "premature closure". This refers to making a diagnosis or an initial impression and then shutting out consideration that the diagnosis may be wrong even as contradictory evidence accumulates.

To mitigate this premature closure,using Groopman's words, the physician needs to:

" repeatedly factor into the analysis the possibility that he is wrong" ... "cogent medical judgments meld first impressions-gestalt-with deliberate analysis." and the physician:

"should be schooled in heuristics-in the power and necessity of shortcuts and in their pitfalls and dangers."

Good diagnosticians need to frequently remind themselves to reconsider the diagnosis as events unfold and test data comes in play asking What else could it be? What have we missed? What is the worst thing it could be?

Basically what we are talking about was nailed by Any Rand when she had her super-heroes say:

"Whenever you think you are facing a contradiction, check your premises, you will find that one of them is wrong." Atlas Shrugged.

For physicians who might want a shorter version ( Dr. Groopman's stated aim was to write a book for layman's consumption) of the key issues with cognitive errors in medical diagnosis, here is an excellent article by Dr. Donald Redelmeier.