The specificity of a test can be described as the proportion of true negatives it detects of all the patients without the target disorder.
It is thus the proportion of patients without the target disorder who have a negative test result.
All negatives are the sum of (detected) true negatives (TN) and (misdiagnosed) false positives (FP).
|Target Disorder Present||Target Disorder Absent|
|Test result positive||True Positive (TP)||False Positive (FP)|
|Test result negative||False Negative (FN)||True Negative (TN)|
Specificity is therefore:
- TN / (TN + FP) x 100%