IFNG and infection: In contrast to the pattern observed for community controls, TST and QFT-IT test responses did not increase with age for contacts of smear-positive cases, suggesting that children of all ages are at high risk for infection in these households Our findings are consistent with those of previous studies of mixed-age populations that used different versions of IFN-γ tests and reported infection rates of 30% to 70% for household contacts (16,20,21) and an association between proximity of an index patient and positive IFN-γ responses (13,14,20).