False positive results may occur if the child cross-reacts with other germs that are antigenically similar to the germs that cause tuberculosis
. These cross-reacting germs belong to the same family of bacteria that cause tuberculosis, and may either be those that are present in air, or those that are atypical - i.e. not like the classical bacteria that cause tuberculosis.
However, even so, a recent conversion from a negative to a positive test cannot be ignored, and I suggest that you go ahead with the INH
therapy. Unless I am mistaken, INH needs to be used with Rifampicin
and both need to be given for 3 months to 6, but never 9 months.