This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bacteria, Subject name: Microbiology
True about Mantoux test: 
Select and explain. 
A. < 5 mm always +ve, B. Usually -ve after treatment, C. Usually read after 48-72 hours, D. False +ve in post measles state
C: Usually read after 48-72 hours
Answer: C: Usually read after 48-72 hours 
Explanation: Ans. is 'c' i.e., Usually read after 48-72 hoursConsidering other choices:(a) >10 mm is positive and 6-9 mm is Equivocal/Doubtful reaction.(b) It becomes positive after exposure to mycobacterium tuberculosis protein either in the form of infection or immunization and remains positive even after treatment.Note - Tuberculin test in Adults is used as Epidemiological marker and in Children is used as diagnostic marker.