What does specificity measure in a serology test?

• A. Ability to obtain negative result when serologically negative
• B. Ability to obtain positive result when the disease is present
• C. Ability to obtain negative result when the disease is present
• D. Ability to obtain positive result when serologically negative

Answer: (A)

Specificity measures how well a test correctly identifies people who do not have the disease. In a serology test, it refers to the proportion of true negatives among all individuals who are serologically negative (truly disease-free). A test with high specificity yields few false positives, meaning it’s unlikely to give a positive result in someone who isn’t actually infected. The other statements describe sensitivity (detecting disease when it’s present) and the idea of false results, which aren’t what specificity gauges.