Which statement best defines sensitivity in diagnostic testing?

• A. Detects disease when it is present
• B. Detects disease when it is absent
• C. Predicts future outcomes
• D. Measures severity

Answer: (A)

Sensitivity measures the test’s ability to detect disease when it is actually present. It’s the true positive rate—among all people who truly have the disease, what proportion test positive? A test with high sensitivity catches most people who are ill, so there are few false negatives. That’s why sensitivity is prioritized in screening: if the test is negative, you can be reasonably confident the disease is not present, though no test is perfect. In contrast, detecting disease when it is absent relates to specificity, prognostic value concerns predicting future outcomes, and measuring severity deals with how advanced or serious the disease is, not whether it’s detected.