TABLE 3.

Sensitivity, Specificity, and Predictive Value Refresher

MeasureDescriptionFormula
SensitivityProbability that result will be positive when disease is presentTP/(TP + FN)
SpecificityProbability that result will be negative when disease is absentTN/(TN + FP)
AccuracyNumber of correct findings(TP + TN)/(TP + TN + FP + FN)
Positive predictive valueProbability that patients with positive result truly have diseaseTP/(TP + FP)
Negative predictive valueProbability that patients with negative result do not have diseaseTN/(TN+FN)
  • TP = patients with positive result who have disease; FN = patients with negative result who have disease; TN = patients with negative result who do not have disease; FP = patients with positive result who do not have disease.