A screening test for cervical cancer has a sensitivity of 80% and specificity of 90%. In a population where the prevalence of cervical cancer is 1%, the Positive Predictive Value (PPV) of this test will be approximately:
- A 80%
- B 7.5% ✓
- C 90%
- D 42%
Correct answer: B. 7.5%
Explanation
In a population of 10,000 with 1% prevalence: True cases = 100, non-cases = 9,900. True positives = 100 × 0.80 = 80; False positives = 9,900 × (1-0.90) = 990. PPV = TP/(TP+FP) = 80/(80+990) = 80/1070 ≈ 7.5%. This demonstrates the critical impact of disease prevalence on PPV — even with excellent sensitivity and specificity, a low-prevalence disease yields poor PPV, resulting in many false positives per true positive. This is why population-wide screening for rare diseases is often not recommended without confirmatory tests.
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.