Which metric equals TN divided by (TN plus FP)?

• A. Diagnostic Specificity
• B. Diagnostic Sensitivity
• C. Positive Predictive Value
• D. Negative Predictive Value

Answer: (A)

Specificity measures how well a test identifies people who do not have the disease. It is the proportion of true negatives among all non-diseased individuals, calculated as TN divided by (TN plus FP). A high specificity means few healthy people are incorrectly labeled as diseased (few false positives). This is different from sensitivity, which uses true positives and false negatives, and from the predictive values: positive predictive value uses true positives and false positives, while negative predictive value uses true negatives and false negatives. Therefore, TN/(TN+FP) corresponds to specificity.