This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Disease Causation, Measurements, Milestones, Subject name: Social & Preventive Medicine
[{'content': 'In a village having population of 1000, we found patients with ceain disease. The results of new diagnostic test on disease are as follows: Test result Disease Present Absent + 180 400 - 20 400 What is the percent prevalence of disease? \nSelect and explain. \nA. 0.2, B. 2, C. 18, D. 20', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Prevalence is defined as all current cases (old + new) at a given point of time. Prevalence = No. of all current cases of a disease at a time/ Estimated total population at that time X 100 In the given question, Test result Disease Present Absent + 180 400 - 20 400 Total 200 800 Thus, Prevalence = 200 / (200 + 800) X 100 = 20%', 'role': 'assistant'}]