Non-clinical sciences/Stats & evidence · Test characteristics

Sensitivity

What it means

TP / (TP + FN) — probability a test is positive in those WITH the disease. A property of the test (not prevalence-dependent). A highly sensitive test, when negative, rules disease OUT (SnNOUT). Good for screening (don't miss cases).

Worked example

D-dimer is sensitive but not specific: a negative result helps exclude PE/DVT; a positive needs imaging.

In the exam

A test rarely misses true cases, so a negative result is reassuring for ruling the disease out — it is used to screen.

What settles it

Sensitivity (SnNOUT, rule-out, screening) vs specificity (SpPIN, rule-in, confirmation); both are test properties independent of prevalence.

Classically confused with

Specificity

Source: StatPearls — Sensitivity and Specificity