This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Screening, Subject name: Social & Preventive Medicine
Positive predictive value is most affected by- 
Select and explain. 
A. Prevalence, B. Sensitivity, C. Specificity, D. Relative risk
A: Prevalence
Answer: A: Prevalence 
Explanation: Ref:Parks 25th edition pg.153 Postitive predictive value depends on prevalence. Note : PPV increases as prevalence increases. PPV decreases as prevalence decreases. But sensitivity and specificity is independent of prevalence.