True about tuberculin test are all except ?

Ans. is `c' i.e., No risk in negative . Persons who have never had contact with tubercle bacilli are tuberculin negative. It means they are susceptible to T.B. infection as they have not developed cell mediated immunity against M. tuberculosis. About other options Option 'a' Indication for chemoprophylaxis by ATT. 1) Contacts of open cases who show recent montoux conversion (option 'a') 2) Children with positive montoux and a TB patient in the family. 3) Neonate of tubercular mother. 4) Patients of leukemia, diabetes, silicosis, or those who are HIV positive but are not energic, or are on coicosteroid therapy who show a positive Mantoux. 5) Patients with old inactive disease who are assessed to have received inadequate therapy. Option 'b' Is paially correct, because positive tuberculin test is not an indication for prophylaxis in all cases, but it is an indication for chemoprophylaxis for the contacts of open cases. Option 'd' Test may be false negative in immunocompromized patients - Ananthanarayan p. 361.