Predictive Value Theory
The diagnostic value of a procedure is defined by its sensitivity, specificity, predictive value and efficiency. The formula are summarized below.
| Test Positive | Test Negative | |
|---|---|---|
| Disease Present | True Positive (TP) | False Negative (FN) |
| Disease Absent | False Positive (FP) | True Negative (TN) |
SENSITIVITY:
Sensitivity of a test is the percentage of all patients with disease present who have a positive test.
SPECIFICITY:
Specificity of a test is the percentage of all patients without disease who have a negative test.
PREDICTIVE VALUE:
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.
TEST EFFICIENCY:
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.
