The optimum sensitivity of 77.2% and specificity of 87.2% of the IL-2/IFN-γ ratio in detecting ATB from LTBI (cut-off value of 1.133) suggested that this ratio may not function as a stand-alone diagnostic indicator of LTBI, but one of the valid methods to distinguish active TB from latent infection. This evidence concerns the gene IFNG and disease arising from reactivation of latent virus.