A test's specificity measures the percentage of individuals without the condition being tested for, who will have a negative test. (A test with high specificity will produce fewer false positive results.)
Where:
- True negative = the individual does not have the disease or illness; results are negative
- False positive = the individual does not have the disease or illness; results are positive
To calculate specificity, use the following formula:
True Negatives (TN)
Divided by True Negatives (TN) plus False Positives (FP)
Times 100
or
[TN ÷ (TN + FP)] x 100
The result is a percentage.
Note: The term specificity (or true negative rate) helps with understanding how well a test identifies true negatives.
