The Acute Mind

Diagnostic Discrimination

Definition

The process of identifying & using key clinical features to distinguish & prioritise between competing diagnoses. It focuses attention on the findings that carry the greatest diagnostic value whilst de-prioritising / discarding those of lesser importance.

​

How to Apply

There are broadly three types:

• Disproportionate sign – probably one of my personal favourite framework and esp. useful in cases of diagnostic uncertainty. Identify the key sign that is disproportionate to the rest of the clinical context – this is often the key clue that points the path to the diagnosis (e.g. disproportionate abdominal pain / lactate, disproportionately raised CRP)

• Red flag or Red herring – signal discrimination particularly useful when patients present with a multitude of symptoms (increasingly common). Through practice, recognising which signs are red herrings otherwise we may become overwhelmed & at risk of ‘barking up the wrong tree’.

• Hallmark features – useful in identifying the key signs specific to the disease in the clinical context (e.g. SOB with raised JVP & oedema – right sided HF, weakness with ptosis but normal reflexes – more likely myasthenia than GBS).