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
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 
Select and explain. 
A. 60%, 80%, B. 80%, 60%, C. 66.6%, 75%, D. 75%, 66.6%
B: 80%, 60%
Answer: B: 80%, 60% 
Explanation: 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%