Sensitivity is defined as which of the following?

Sensitivity is defined as which of the following?

• A. Probability a test is positive given disease
• B. Probability a test is negative given disease
• C. Probability a test is positive given no disease
• D. Probability a test is negative given no disease

Answer: (A)

Sensitivity is the probability that the test is positive in people who truly have the disease. It tells you how good the test is at detecting disease when it’s actually present, and is calculated as true positives divided by all people with the disease (TP + FN). Clinically, a high sensitivity means few missed cases (low false negatives), which is important for screening. The other ideas refer to different measures: the chance of a negative result among those with disease is the false negative rate (1 minus sensitivity); the chance of a positive result among those without disease is the false positive rate (1 minus specificity); and the chance of a negative result among those without disease is specificity.

Sensitivity is the probability that the test is positive in people who truly have the disease. It tells you how good the test is at detecting disease when it’s actually present, and is calculated as true positives divided by all people with the disease (TP + FN). Clinically, a high sensitivity means few missed cases (low false negatives), which is important for screening. The other ideas refer to different measures: the chance of a negative result among those with disease is the false negative rate (1 minus sensitivity); the chance of a positive result among those without disease is the false positive rate (1 minus specificity); and the chance of a negative result among those without disease is specificity.