Specificity measures?

• A. Proportion of diseased individuals who test positive
• B. The aesthetic quality of the test
• C. The ability to identify those with the disease
• D. The test’s ability to correctly identify individuals without the disease

Answer: (D)

Specificity measures the test's ability to correctly identify individuals who do not have the disease. It is calculated as true negatives divided by the sum of true negatives and false positives, so a high specificity means few false positives—healthy people are unlikely to be mislabeled as diseased. The option about the proportion of diseased individuals who test positive describes sensitivity, not specificity, and the option about the ability to identify those with the disease also points to sensitivity. The statement about the test’s aesthetic quality is not a diagnostic measure. So the correct measure is the test’s ability to correctly identify individuals without the disease.