They measure the T-cell IFNγ production after 16 to 24h of contact with M. tuberculosis specific antigens coded by the region of deletion 1 or RD1 (ESAT-6 + CFP-10 for T-SPOT-TB, and ESAT-6 + CFP-10 + Tb7.7 for QF-TB-IT). This evidence concerns the gene IFNG and tuberculosis.