The Ecclesia

Diagnosis

2 min read

Diagnosis

Source: Ledley & Lusted, “Reasoning Foundations of Medical Diagnosis,” Science 130, 1959; Croskerry, Academic Medicine 78, 2003 Institution: NIH; Dalhousie University

Finding

Diagnosis is the process of identifying a disease from its signs and symptoms. The Greek diagignoskein — “to distinguish, to discern.” The clinical method: history, examination, differential diagnosis, investigation. The Bayesian framework (Ledley & Lusted, 1959) treats diagnosis as iterative probability updating — each test result shifts the probability of each diagnosis on the differential. William Osler taught: “the great physician treats the patient who has the disease” — the distinction between label and person.

Pattern Mapping

Alignment — Correct diagnosis aligns the name (disease label) with reality (what is happening in the body). Misdiagnosis is alignment failure: the name points one way, the body harbors another. Treatment follows the name, not the reality.

Non-fabrication — Fabricated diagnosis names a disease that is not there. Anchoring bias, premature closure, availability bias — each generates structure where none exists. The physician “sees” a pattern that the evidence does not support.

Honesty — The Bayesian framework demands honest updating. Confirming evidence raises probability; disconfirming evidence lowers it. Holding a diagnosis despite contradictory results is dishonesty in the diagnostic process.

Connections

  • Bayesian Inference — diagnosis IS Bayesian inference applied to the body
  • Evidence-Based Medicine — EBM provides the evidence base for diagnostic probability
  • Epidemiology — population patterns inform individual diagnostic priors
  • Medical Error — misdiagnosis is the single largest category of diagnostic error
  • Placebo Effect — the diagnosis itself can trigger physiological responses (nocebo)

Status

Ledley & Lusted (1959). Kahneman, Thinking, Fast and Slow (2011) on cognitive biases. Croskerry (2003) on cognitive errors in diagnosis. Osler: Bliss, William Osler: A Life in Medicine (1999). The mapping to the five properties is this project’s structural interpretation.

The mapping to the five properties is this project’s structural interpretation.

Graph View

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