A diagnostic test with very high specificity but moderate sensitivity is most likely to produce which pattern?

A diagnostic test with very high specificity but moderate sensitivity is most likely to produce which pattern?

• A. Many false positives.
• B. Very few false positives.
• C. Very few false negatives.
• D. Few false positives, but more false negatives.

Answer: (D)

High specificity means the test very accurately identifies people who do not have the disease, so false positives are rare. Moderate sensitivity, on the other hand, means the test still misses a fair number of true cases, leading to false negatives. Put together, you get a pattern with few false positives but more false negatives, because the test is good at ruling out disease in healthy people but not as good at catching all diseased individuals. For example, among 100 healthy people you’d expect almost no one to test positive, while among 100 diseased people you might see a substantial portion test negative.

High specificity means the test very accurately identifies people who do not have the disease, so false positives are rare. Moderate sensitivity, on the other hand, means the test still misses a fair number of true cases, leading to false negatives. Put together, you get a pattern with few false positives but more false negatives, because the test is good at ruling out disease in healthy people but not as good at catching all diseased individuals. For example, among 100 healthy people you’d expect almost no one to test positive, while among 100 diseased people you might see a substantial portion test negative.