This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Social & Preventive Medicine
True statement regarding `tuberculine test' is ? 
Select and explain. 
A. Used for diagnosis of TB, B. Measures incidence of disease, C. More than 1 Omm induration in 72 hrs. indicates positive test, D. Measure immunity status
C: More than 1 Omm induration in 72 hrs. indicates positive test
Answer: C: More than 1 Omm induration in 72 hrs. indicates positive test 
Explanation: Ans. is 'c' i.e., More than 10 mm induration in 72 hrs indicates positive test Repeat tuberculin test (two step testing) o Induration is measured, erythtna is not taken into account. Uses of tuberculin test o Diagnosing active infection in infants and young children. o Measure prevalence of infection. o Select susceptibles. o As an indication of sucessful vaccination.