Core IM Hoofbeats: A 36F with weakness

May 2, 2018

CORE IM Podcast podcast 2 min read

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By John Hwang MD, Cindy Fang MD, Neha Sathe MD,  Michael P. Janjigian MD || Audio Editing and Graphic by Amy Ou, MD

Time Stamps

  1. Part 1 Case (2:05)
  2. Framing bias (7:07)
  3. Data-driving reasoning  (11:48)
  4. Hypothesis-driven approach (12:38)
  5. Periodic paralysis syndromes (16:08)
  6. Representativeness heuristic (17:26)
  7. Part 2 Case (20:51)
  8. Pivot Points (31:36)
  9. Diagnosis (35:55)
  10. Take aways (37:20)

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Show Notes

  1. A clinician employing “data-driven reasoning” (“working forwards”) starts with raw clinical data and tries to arrange them into meaningful patterns to build hypotheses about the patient’s illness.
  2. A clinician employing “hypothesis-driven reasoning” (“working backwards”) starts with a clinical problem, generates a series of hypotheses about the patient’s illness, then tests each of these against the available clinical data.
  3. Patients with hypokalemic periodic paralysis syndromes suffer episodic weakness due to massive intracellular shifts of potassium, often triggered by periods of stress or exercise; they can be entirely asymptomatic between episodes.
  4. The representativeness heuristic is a mental shortcut in which a clinician judges the probability of a diagnosis based on the similarity of the patient to the clinician’s mental picture (i.e. stereotype) of that diagnosis.
  5. Base-rate neglect refers to the tendency of clinicians to rely on information specific to a case (e.g. using the representativeness heuristic) to judge the likelihood of a given diagnosis, while ignoring the actual prevalence of that diagnosis.
  6. It is not uncommon for patients with Sjogren’s syndrome to develop renal manifestations of their disease; this can take the form of subclinical lab abnormalities, nephrogenic diabetes insipidus, progressive renal insufficiency, and chronic tubular or interstitial nephritis, with or without renal tubular acidosis.
  7. The combination of hypokalemia and non-anion gap metabolic acidosis is a diagnostically meaningful pattern, characteristic of two disease processes: diarrhea and renal tubular acidosis.

References

  1. Patel VL, Arocha JF, Kaufman DR. Diagnostic Reasoning and Medical Expertise. Psychology of Learning and Motivation – Advances in Research and Theory. 1994;31(C):187-252. Available from, DOI: 10.1016/S0079-7421(08)60411-9.
  2. Kassirer JP, Kopelman RI. Learning Clinical Reasoning. Baltimore: Williams and Wilkins, 1991.
  3. Zayac A, Shah R, Shah M, Umar J, Bansal N, Dhamoon A. Thyrotoxic hypokalemic periodic paralysis. QJM: monthly journal of the Association of Physicians 2016;109:613-4.
  4. Kahneman D, Tversky A. On the psychology of prediction. Psychological Review 1973;80:237-51.
  5. Arocha JF, Wang D, Patel VL. Identifying reasoning strategies in medical decision making: a methodological guide. Journal of biomedical informatics 2005;38:154-71.
  6. Francois H, Mariette X.  Renal involvement in primary Sjögren’s syndrome.  Nat Rev Nephrol.  2016 Feb; 12(2):82-93.
  7. Kronbichler A, Mayer G.  Renal involvement in autoimmune connective tissue diseases.  BMC Med. 2013; 11(95).