Differential Diagnosis Bank

What it is

A differential diagnosis is the set of conditions that could account for a patient's presentation, held open deliberately while evidence accumulates. It is a discipline against premature closure — the habit of settling on the first plausible answer and then reading everything afterwards as confirmation.

It is a working tool, not a conclusion. Items enter it because they are possible, and leave it because history, examination or investigation has made them unlikely — not because they felt improbable at the outset.

How a differential is built

Start from the presentation, not the diagnosis

A differential is built around what the patient actually has — a symptom, a sign, an abnormal result — not around a condition you already suspect. Anchoring on a diagnosis first is how alternatives get missed.

Widen before you narrow

The point of a differential list is to make the possibilities explicit before history, examination and investigation cut it down. A list you generate after deciding is not a differential.

Rule out the dangerous before the likely

Common things are common, but the ones that kill quickly come first. Chest pain is usually musculoskeletal and occasionally an aortic dissection; the order you exclude them in is not the order of frequency.

Let the context reweight the list

Age, sex, comorbidity, medication, travel, occupation and pregnancy all change which items matter. The same presentation in two patients is not the same problem.

Revisit when the picture changes

A differential is a working document. New findings, a failed treatment or a changed trajectory are reasons to reopen it rather than defend the original answer.

What this bank covers

194 presentations indexed by sign, symptom and abnormal finding, across every system. A selection of what is included: