True statement regarding `tuberculine test' is ?

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.