A diagnostic test with high sensitivity is most useful for ruling out disease when negative.

• A. True
• B. False
• C. Not applicable
• D. Depends on disease prevalence

Answer: (A)

High sensitivity means the test catches most people who have the disease, so there are few false negatives. When the result is negative, the chance that the disease is actually present is very low, making a negative result reliable for ruling out the disease. This is the idea behind SnNout: a Highly Sensitive test, when Negative, rules out disease. Specificity, not sensitivity, governs ruling in with a positive result. While prevalence affects the predictive values of a test, the rule-out usefulness of a negative result is tied to sensitivity, not how common the disease is.