Physicians, Probabilities, and Populations—Estimating the Likelihood of Disease for Common Clinical Scenarios

Arjun K. Manrai

doi:10.1001/jamainternmed.2021.0240

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April 5, 2021

Physicians, Probabilities, and Populations—Estimating the Likelihood of Disease for Common Clinical Scenarios

Arjun K. Manrai, PhD^1,2

Author Affiliations Article Information

¹Computational Health Informatics Program, Boston Children’s Hospital, Boston, Massachusetts
²Department of Biomedical Informatics, Harvard Medical School, Boston, Massachusetts

JAMA Intern Med. 2021;181(6):756-757. doi:10.1001/jamainternmed.2021.0240

An enviably close and influential collaboration during the 1970s between the psychologists Amos Tversky and Daniel Kahneman reshaped our beliefs about intuitive probabilistic reasoning. One of their many contributions was a demonstration of the base-rate fallacy, the tendency for people to neglect prior probabilities, or “base rates,” when calculating the chances of an event given more specific data.¹ For example, the chances that a patient has a disease being tested reflects not only the test result and the test’s sensitivity and specificity, but also the relevant base rate, which is the prevalence of disease in a specific population.

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June 8, 2021

gestalt thinking is still useful

James Wright, MD | Amita St Joseph Medical Center, Joliet, IL

One unavoidable problem with studies like the one so well performed and reported by Morgan, et al, is that the study participants are asked to make judgments on stories, descriptions, vignettes...not real, live patients. There is value in this approach, but I fear that it misses the knowledge of, and the impression left by, evaluating a patient who is being interviewed and examined by the practitioner in the here and now. This is of course the reality of the great majority of diagnostic interactions that occur on a day to day basis.
I still remember from medical school, during numerous case presentations before an attending, the rejoinder by said attending to "Look at the patient". When the data pointed to a diagnosis, or a sense of urgency, that just didn't seem quite right, it was always a good idea to circle back and "look at the patient". And while this remains good advice, it's not as useful for practitioners in training who haven't looked at that many patients with particular presenting complaints or predicaments, whether it be chest pain, dyspnea, concern about breast cancer, anxiety or numerous others.
The importance of this intimate interaction between patient and provider has become much more obvious to me after a year of "virtual" visits; interactions in which, at best, the provider can only see and talk with a patient on a computer.
After a long career in internal medicine, I have had the opportunity to "look at" a great many patients. I believe that providers, like myself, who have practiced for many years, often develop a gestalt appraisal 'system' for people presenting in common scenarios. These systems are not perfect and vary in accuracy. They are personal to the practitioner, and often unrecognized by the provider, which can be problematic.
My point is that this "gestalt" picture, obtained by a seasoned practitioner, is often very incisive (intuitive?) and can lead to a correct diagnosis early in the evaluation. It can also help to avoid a needless, and often expensive, work up or at least focus the evaluation and limit the not only monetary expense of the work-up.

CONFLICT OF INTEREST: None Reported

Physicians, Probabilities, and Populations—Estimating the Likelihood of Disease for Common Clinical Scenarios

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