This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Sensitivity, Specificity, PPV, NPV, Subject name: Social & Preventive Medicine
[{'content': 'Calculate Sensitivity and Specificity of ELISA in a population screened for HIV. Data is given below HIV Present HIV Absent ELISA +ve 80 40 ELISA -ve 20 60 \nSelect and explain. \nA. 60%, 80%, B. 80%, 60%, C. 66.6%, 75%, D. 75%, 66.6%', 'role': 'user'}, {'content': 'Answer: B \nExplanation: HIV Present HIV Absent ELISA + ve 80 = a 40 =b ELISA -ve 20 = c 60 =d Sensitivity = a/a+c x 100 = 80/100 X 100 = 80% Specificity = d/ b+d x 100 = 60/100 X 100 = 60% PPV 80/120 X 100 = 66% NPV 60/80 X 100 = 75%', 'role': 'assistant'}]