Specificity of a test refers to its ability to detect the following:

Specificity of a test is defined as the percentage of persons without the disease of interest who have negative test results, i.e., true negatives. Specificity is calculated as follows: Sensitivity is defined as the ability of the test to identify correctly all those who have the disease i.e. true positives. Ref: Greenberg R.S., Daniels S.R., Flanders W.D., Eley J.W., Boring, III J.R. (2005). Chapter 6. Diagnostic Testing. In R.S. Greenberg, S.R. Daniels, W.D. Flanders, J.W. Eley, J.R. Boring, III (Eds), Medical Epidemiology, 4e.