Median IFN-γ responses differed significantly in culture-positive vs. -negative individuals when measured using TSPOT.TB [111 (IQR: 500-194) vs. 32 (10–104) SFC⋅10−6 PBMCs; p<0.01] and QFT-GIT [2.2 (0.6, 5.2) vs. 0.7 (0.1, 3.1) international units (IU)⋅ml−1; p<0.01], but not in response to PPD [100 (36, 161) vs. 86 (16, 157) SFC⋅10−6 PBMCs; p = 0.28]. This evidence concerns the gene IFNG and tuberculosis.