IFNG and tuberculosis: The T-SPOT assay that analyses IFNg producing T Spot-forming cells (sfc) isolated from PBMCs for their response to TB antigens (Ag); secreted antigenic target 6 (ESAT-6) and culture filtrate protein 10 (CFP-10) and phytohaemagglutinin (PHA) TB Ags ratio to predict LTB infection.