A new diagnostic test for diabetes is evaluated in 1000 individuals: 200 have diabetes (gold standard). The test is positive in 180 of the 200 diabetics and in 60 of the 800 non-diabetics. What is the Positive Predictive Value (PPV)?
- A 90%
- B 75% ✓
- C 92.5%
- D 75.0%
Correct answer: B. 75%
Explanation
True Positives (TP) = 180, False Positives (FP) = 60. PPV = TP / (TP + FP) = 180 / (180 + 60) = 180/240 = 0.75 = 75%. Sensitivity = 180/200 = 90%; Specificity = 740/800 = 92.5%. PPV depends critically on disease prevalence — even with high sensitivity/specificity, PPV falls in low-prevalence populations.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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