Specificity (Sp)
The percentage of patients without a disorder who have a negative test for that disorder is a test’s specificity.
True negative rate. The ability to detect health (nondisease). Sp is the probability that among people who don’t have the disease, the disease will be excluded by the test. A highly specific test is great for confirming the diagnosis. It may have false-negatives but doesn’t call anyone sick who is actually healthy (i.e. low false-positive rate). Mathematically, Sp is the number of true negatives divided by the number of people without the disease. Sp = D/( B + D)