Sensitivity of a diagnostic test is defined as what?

• A. True positives divided by (true positives plus false negatives)
• B. True negatives divided by (true negatives plus false positives)
• C. True positives divided by (true positives plus false positives)
• D. False negatives divided by (true positives plus false negatives)

Answer: (A)

Sensitivity measures the test’s ability to identify those who actually have the disease. It answers: among people with the condition, what fraction test positive? It is calculated as true positives divided by the sum of true positives and false negatives. This reflects how well the test catches real cases and minimizes missed diseases. For context, specificity uses true negatives over (true negatives plus false positives), while the false negative rate uses false negatives over (true positives plus false negatives), and precision (positive predictive value) uses true positives over (true positives plus false positives).