How is sensitivity defined in test characteristics?

• A. The % of healthy individuals who would have a normal result
• B. The percentage of diseased individuals who test positive
• C. The % of individuals with the target condition who would have an abnormal or positive result
• D. The likelihood ratio of a positive test

Answer: (C)

Sensitivity measures how reliably a test identifies disease when it is actually present. It is the proportion of people who have the target condition who yield a positive (abnormal) result on the test. In other words, among all individuals with the condition, what fraction tests positive? This is why the statement describing the percentage of those with the condition who have an abnormal or positive result is the best fit.

For contrast, specificity refers to how well a test identifies those without the condition—essentially, the percentage of healthy people who test negative. The likelihood ratio of a positive test combines sensitivity and specificity to show how much a positive result changes the odds of disease, rather than defining sensitivity itself.