Blood-based IGRA, including QuantiFERON TB Gold In-Tube (Qiagen; QFT-GIT) and T-SPOT.TB (Oxford Immunotec), measures in vitro IFN-γ production upon antigen stimulation of the whole blood by enzyme-linked immunosorbent assay (ELISA) or peripheral blood mononuclear cells (PBMC) by enzyme-linked immunospot (ELISPOT) assay, respectively [53]. Here, IFNG is linked to tuberculosis.