A screening test for cervical cancer (VIA) has a sensitivity of 80% and specificity of 85%. In a population with 5% prevalence of disease, what is the positive predictive value (PPV)?
- A Approximately 22% ✓
- B Approximately 50%
- C Approximately 80%
- D Approximately 95%
Correct answer: A. Approximately 22%
Explanation
Using Bayes' theorem with prevalence 5%, sensitivity 80%, specificity 85%: TP = 0.05×0.80 = 0.04; FP = 0.95×0.15 = 0.1425; PPV = 0.04/(0.04+0.1425) ≈ 0.04/0.1825 ≈ 22%. This illustrates that even a good screening test has low PPV when applied to a low-prevalence population, necessitating confirmatory testing. PPV increases when the test is applied to higher-risk populations.
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.