Sunday, August 27, 2006

heuristics and statistics-we need and use both in medicine

In spite of at least one terrible publication to the contrary-the criticism of which is reviewed here- there can be little doubt that experienced clinicians perform better than do novices. Experience and practice really no matter.During the five to ten years it seems to take for a recent medical graduate to become at least a low level expert basically no time is spent on courses on medical decision making.

Does the experienced clinician talk about or think about likelihood ratios or prior probabilities? Does he explicitly use equations to determine positive predictive values etc? Not the ones I have been associated with. What the experienced docs seem to deal in mainly are heuristics. These are rules of thumb,short cuts, and simple judgments that operate in many of the decisions that physicians make.

Dr. Pat Croskerry published an interesting article in the Canadian Journal anesthesiology ( vol. 52:6 p.r1) in which he discusses decision making. He does this from the viewpoint of anesthesiology but it has broad application to medical decision making in general.

His major point is that physicians make many decisions through the mechanisms of heuristics and while they often are effective there are cognitive impediments that limit their usefulness. We need to be aware of those mental tendencies so that we can compensate for them .One example, about which I have written earlier, is "premature closure"., i.e. making a diagnosis and then shutting out consideration that it could be incorrect even as evidence to the contrary accumulates. He mentions many other cognitive tendencies which he refers to as "cognitive dispositions to respond" (CDRs) rather then the earlier tendency to label them as biases or fallacies.Some have intriguing names such as "playing the odds", "Sutton's Slip" and "ego bias". I have not had time yet to research what those terms refer to but some of them may be the topic of a later posting.

His position is that doctors do not typically think in a formalized, statistical manner using formulas which dispassionately weigh the evidence and we should recognize that fact of life and learn about and make efforts to control the CDRs in order to better harness our use of heuristics.

Statistical analysis is an essential element in clinical research but many of the decisions we make in the heat of the clinical battles that take place every day rely on mental processes that seem to have little to do with statistics.

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