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Building a differential

7 minute read

Mechanism first, then probability, then danger

Generate by mechanism (for dyspnea: cardiac, pulmonary, hematologic, metabolic, neuromuscular) so the list has skeleton rather than free association. Then rank twice: once by likelihood, once by danger. The workup must cover the top of both lists, which is why 'common things are common' and 'rule out the killers' are both true and neither is sufficient.

Re-ranking is the skill

A differential earns its keep when new data re-sorts it visibly. The Differential Builder keeps your list on screen as results arrive precisely so the re-sort becomes a habit rather than an accident.

Pearls

  • A differential of one is a bet, not a differential.
  • Write the dangerous item down even at low probability; the list is your handover's safety net.

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Take it further

Copy this page as study notes, then paste them into QSpace for practice questions or AnkiGen for flashcards.

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