Two common metrics used to compare diagnostic tests are sensitivity and specificity. Sensitivity is the probability a patient with a disease tests positive, while specificity is the probability a patient with the disease will test negative.

(Original figure)

Sensitivity = TP/(TP+FN)
Specificity = TN/(TN+FP)

Sensitivity and specificity are static values for any given application.

(Original figure)

Raising a cutoff value will favor specificity in exchange for a poorer sensitivity. Lowering a cutoff value (or coming up with a new high-sensitivity troponin assay, for example) does the opposite.

A brief aside: