|Test Positive||Test Negative|
|Disease Present||True Positive (TP)||False Negative (FN)|
|Disease Absent||False Positive (FP)||True Negative (TN)|
Sensitivity of a test is the percentage of all patients with disease present who have a positive test.
__TP___ X 100 = Sensitivity (%)
TP + FN
Specificity of a test is the percentage of all patients without disease who have a negative test.
__TN___ X 100 = Specificity (%)
FP + TN
The predictive value of a test is a measure (%) of the times that the value (positive or negative) is the true value, i.e. the percent of all positive tests that are true positives is the Positive Predictive Value.
__TP___ X 100 = Predictive Value of a Positive Result (%)
TP + FP
__TN___ X 100 = Predictive Value Negative Result (%)
FN + TN
The efficiency of a test is the percentage of the times that the test give the correct answer compared to the total number of tests.