Quick Review Cards for Medical Laboratory Science

Diagnostic Value of a Test Laboratory Operations Review 58

CHARACTERISTIC EXPLANATION

True positive (TP) Pos result in patient who has the disease

False positive (FP) Pos result in patient who doesn’t have the disease

True negative (TN) Neg result in patient who doesn’t have the disease

False negative (FN) Neg result in patient who does have the disease

Diagnostic sensitivity * % of population with the disease that test pos

TP / (TP + FN) × 100

Diagnostic specificity * % of population without the disease that test neg

TN / (TN + FP) × 100

Positive predictive value * (PPV) % of time that a pos result is correct

TP / (TP + FP) × 100

Negative predictive value * (NPV) % of time that a neg result is correct

TN / (TN + FN) × 100

*Values are determined by manufacturer. Information helps physicians interpret results.