Which statement correctly defines sensitivity and specificity in diagnostic testing?

• A. Sensitivity is the ability to identify true positives; Specificity is the ability to identify true negatives.
• B. Sensitivity measures false positives; Specificity measures false negatives.
• C. Both sensitivity and specificity measure precision only.
• D. Sensitivity equals specificity in all diagnostics.

Answer: (A)

At the heart of this concept is how a diagnostic test performs in detecting disease. Sensitivity is the proportion of people who truly have the disease who test positive, focusing on catching true positives. Specificity is the proportion of people who truly do not have the disease who test negative, focusing on correctly ruling out disease among true negatives. So a statement that defines sensitivity as the ability to identify true positives and specificity as the ability to identify true negatives is exactly describing these ideas. For context, if 20 of 100 people have the disease and 15 are correctly identified as positive, the sensitivity is 75%. If 80 people are disease-free and 70 are correctly identified as negative, the specificity is 87.5%. The other options mix up false positives and false negatives, or claim something like precision, or assert equality across all diagnostics—none of which accurately describe what sensitivity and specificity measure.