IFNG and tuberculosis: To examine the potential of the IGRA as a surrogate for treatment response among young immunocompetent patients with TB, we evaluated the sequential changes in the interferon-gamma (IFN-γ) level measured by the QuantiFERON-TB Gold In-tube (QFT-GIT; Cellestis, Victoria, Australia) assay in immunocompetent adults with TB, but with no underlying disease.