IFNG and tuberculosis: The logistic regression analysis also shown that the positive IL-2/IFN-γ ratios are associated with risk factors for active TB in HHC group including the variable “exposure≧90 hours” (OR:6.7, 95%CI:1.0–23.9; p = 0.029) and “smear grade +++” (OR:4.8, 95%CI:1.0–12.5; p = 0.037).