This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Screening for Disease, Subject name: Social & Preventive Medicine
Numerator in calculating positive predictive value - 
Select and explain. 
A. True positive, B. False positive, C. True negative, D. False negative
A: True positive
Answer: A: True positive 
Explanation: Ans. is 'a' i.e., True positive Sensitivity =Number of true positive--------------------------------------------Number of true positives + Number of false negative Specificity =Number of true negatives--------------------------------------------Number of true negative + number of false positives. Positive predictive value = -True positive--------------------------True positive + False positive Negative predictive value =True negative--------------------------True negative + False negative