A new cardiac enzyme test for MI has a sensitivity of 90% and specificity of 85%. When used in an emergency department where the prevalence of MI is 40%, the Negative Predictive Value (NPV) of this test is approximately:
- A 87%
- B 95%
- C 91% ✓
- D 83%
Correct answer: C. 91%
Explanation
NPV = TN / (TN + FN). Using 1000 people with 40% prevalence: 400 diseased, 600 non-diseased. TP = 0.90 × 400 = 360; FN = 40; TN = 0.85 × 600 = 510; FP = 90. NPV = TN/(TN+FN) = 510/(510+40) = 510/550 ≈ 92.7%, closest to 91%. High NPV with high sensitivity means negative results reliably exclude disease, useful in ruling out serious conditions.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.