What is the difference between sensitivity and specificity?

What is the difference between sensitivity and specificity?

• A. Sensitivity is the true positive rate, while specificity is the true negative rate.
• B. Sensitivity measures how often tests identify negatives.
• C. Specificity measures the rate of false positives.
• D. Both concepts describe the same property.

Answer: (A)

Sensitivity and specificity describe different performance aspects of a diagnostic test. Sensitivity is the true positive rate: among people who actually have the disease, what proportion test positive? It shows how well the test catches disease when it’s present. Specificity is the true negative rate: among people who do not have the disease, what proportion test negative? It reveals how well the test correctly rules out disease when it’s absent. The best statement is that sensitivity is the true positive rate and specificity is the true negative rate. One option would misstate sensitivity as measuring negatives, which isn’t correct because that would refer to identifying non-disease cases. Another option would say specificity measures the rate of false positives; in fact, specificity is about true negatives, while the rate of false positives is 1 minus specificity. Understanding these distinctions helps in choosing tests for screening (favor sensitivity) versus confirmation (favor specificity).

Sensitivity and specificity describe different performance aspects of a diagnostic test. Sensitivity is the true positive rate: among people who actually have the disease, what proportion test positive? It shows how well the test catches disease when it’s present. Specificity is the true negative rate: among people who do not have the disease, what proportion test negative? It reveals how well the test correctly rules out disease when it’s absent.

The best statement is that sensitivity is the true positive rate and specificity is the true negative rate. One option would misstate sensitivity as measuring negatives, which isn’t correct because that would refer to identifying non-disease cases. Another option would say specificity measures the rate of false positives; in fact, specificity is about true negatives, while the rate of false positives is 1 minus specificity. Understanding these distinctions helps in choosing tests for screening (favor sensitivity) versus confirmation (favor specificity).