This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Social & Preventive Medicine
[{'content': 'Positive predictive value is most affected by ? \nSelect and explain. \nA. Prevalence, B. Sensitivity, C. Specificity, D. Relative risk', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., Prevalence", 'role': 'assistant'}]