This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Screening, Subject name: Social & Preventive Medicine
Predictive value indicating positive test in a screening modality is calculated by: 
Select and explain. 
A. TP/TP+FP*100, B. TN/TN+FN *100, C. TP/TP+FN*100, D. TN/FP+TN*100
A: TP/TP+FP*100
Answer: A: TP/TP+FP*100 
Explanation: Ans. (a) TP/TP+FP*100SENSITIVITYTP------TP+ FNx 100PREDICTIVE VALU OF A NEGATIVE TESTTN------TN+FNx 100SPECIFICITYTP------FP+ TNx 100% OF FALSE NEGATIVESFN------TP+ FNx 100PREDICTIVE VALU OF A POSITIVE TESTTP------TP+ FPx 100% OF FALSE POSITIVESTN------FP+ TNx 100