IFNG and infection: However, a sensitivity analysis carried out among the Zambian cohort using calculated IFN-γ responses (therefore including participants with responses >10 IU/ml) showed a mean [TB2-TB1] differential in recent infection of 0.45 IU/ml, which was significantly higher than in remote infection -0.05 IU/ml (p = 0.015) (S4 Fig).