EET PG Medical – 2020 – Question – 120
CA-125 is a marker for the screening of ovarian cancer. To characterize this test, histopathological confirmation of ovarian cancer was done in a cohort of patients. 60/100 women who tested positive for this test had ovarian cancer and 20/100 women who tested negative had ovarian cancer. What is the negative predictive value of this test?
a) 20/100
b) 40/100
c) 60/100
d) 80/100
Correct Answer – D
Ans: D. 80/100
Negative predictive value (NPV): Ability of a screening test to identify correctly all those who don’t have the disease, out of all those who test negative on a screening test.
Negative Predictive Value (NPV) = Number of true negatives/(Number of true negatives + number of false negatives).
Disease present Disease absent
Test Positive 60 (a: TP) 40 (b: FP)
Test Negative20 (c: FN) 80 (d: TN)
Total 80 120
True negatives = 80
Total negatives = 100
Negative predictive value = 80/100 = 80%.
