Two new psychology papers on diagnosis

Jain, Bimal P.,M.D. BJAIN at PARTNERS.ORG
Fri Dec 16 13:32:14 UTC 2016


Ben Rottman's two papers raise interesting and important issues about role of probability in diagnosis. We briefly discuss findings in our two recent papers on method of diagnosis.
We investigated the method of diagnosis employed by experienced clinicians for diagnosis in real patients in 50 CPCs and found it to  consist of the following steps:
1.A number of diseases are suspected from the presentation.
2.Each disease is formulated as a diagnostic hypothesis that is as an assumption which may or may not be correct.
3. Each suspected disease is evaluated for its presence in the given patient in terms of its likelihood given findings in the patient.
4. The disease with the greatest likelihood is diagnosed to be present.
With this method, a correct diagnosis is made in 49 out of 50 CPCs.
We find that prior probability is not even mentioned in any CPC let alone employed as prior evidence for a disease in any CPC.
In a subsequent paper, we discuss why probability does not play any significant role in diagnosis in a CPC.
A probability, being a frequency in a population represents evidence only in a large group and therefore it plays a key role in inference in life insurance business for example in which the aim is accuracy in the long run in a large group. Errors in some individual persons are expected and tolerated in this business.
In diagnosis, on the other hand, our aim is correct determination of a disease in every individual patient in whom a probability represents not evidence but chance. The only role of prior probability in diagnosis, we believe is in setting the order in which various suspected diseases are tested.
The probabilistic or Bayesian method with its notion of prior probability as prior evidence may encourage failure to suspect a disease with an atypical presentation leading to diagnostic error.
We believe the prescription of the probabilistic method for diagnosis should be re-evaluated as this has important implications for teaching diagnosis to novice physicians and for developing computer systems which aid physicians in diagnosis.

Bimal P Jain MD
Northshore Medical Center
Lynn MA 01904.

-----Original Message-----
From: Ben Rottman [mailto:rottman at PITT.EDU] 
Sent: Thursday, December 15, 2016 11:14 AM
To: IMPROVEDX at LIST.IMPROVEDIAGNOSIS.ORG
Subject: [IMPROVEDX] Two new psychology papers on diagnosis

Dear ImproveDX Readers,

I recently published two new psychology papers on diagnosis that might interest some of you. One paper investigates the use of base rate (disease prevalence) knowledge when forming a preliminary diagnosis. The other investigates how well physicians make post-test judgments in reference to their own pre-test judgments and beliefs about the sensitivity and specificity of the test. I believe that these papers provide some of the strongest evidence that physicians actually can be fairly rational (in terms of Bayes’ rule) when forming diagnoses.

The main limitation of these papers is that they both involve reasoning about vignette cases, not real patients in-person. The main strength is that they investigate physicians’ use of their own beliefs about disease prevalence, which has rarely been done in the past, and probably explains why physicians often look so irrational in prior studies.

Paper 1 on Preliminary Diagnoses: Open Access Link
http://cognitiveresearchjournal.springeropen.com/articles/10.1186/s41235-016-0005-8
Paper 2 on pre-test post-test diagnostic updating:
http://link.springer.com/article/10.3758%2Fs13421-016-0658-z
or if you have trouble downloading it you can get it here:
http://www.lrdc.pitt.edu/rottman/

Feel free to share your thoughts on the listserv or to me via email.

Ben Rottman
Assistant Professor Psychology, University of Pittsburgh rottman at pitt.edu

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ATTACHMENT:
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Name: [Diagnosis] Why is diagnosis not probabilistic in clinical-pathological conference (CPCs)- Point.pdf Type: application/pdf Size: 96716 bytes Desc: [Diagnosis] Why is diagnosis not probabilistic in clinical-pathological conference (CPCs)- Point.pdf URL: <../attachments/20161216/eb8bd1b1/attachment-0001.pdf>


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