If a diagnostic test has high specificity, what is the expected rate of false positives?

If a diagnostic test has high specificity, what is the expected rate of false positives?

• A. High rate
• B. Low rate
• C. Unknown
• D. Not applicable

Answer: (B)

High specificity means the test is very good at ruling out disease in people who don’t have it. Specificity is the proportion of true negatives among all without the disease, so a high value translates to few false positives. The false positive rate is 1 minus specificity, so a highly specific test yields a low rate of false positives. For example, a specificity of 95% would mean about 5% of healthy individuals might test positive.

High specificity means the test is very good at ruling out disease in people who don’t have it. Specificity is the proportion of true negatives among all without the disease, so a high value translates to few false positives. The false positive rate is 1 minus specificity, so a highly specific test yields a low rate of false positives. For example, a specificity of 95% would mean about 5% of healthy individuals might test positive.