Which of the following statements about the Negative Predictive Value (NPV) of a screening test is correct?

• A NPV depends only on test sensitivity and never on specificity
• B NPV increases as disease prevalence in the screened population increases
• C NPV is independent of disease prevalence
• D NPV increases as disease prevalence in the screened population decreases ✓

Explanation

Predictive values depend on prevalence. When prevalence is low, most people tested are truly free of disease, so among all negatives the proportion who are truly disease-free, the NPV, becomes very high. This is why a negative result is more reassuring in a low-prevalence setting. Option B describes the behaviour of PPV, which rises with prevalence. NPV also depends on specificity, since false positives enter the denominator of the NPV calculation.

Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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