Question
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
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Correct Answer » D Explanation |
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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 Negative | 20 (c: FN) | 80 (d: TN) |
| Total | 80 | 120 |
- True negatives = 80
- Total negatives = 100
- Negative predictive value = 80/100 = 80%.