QuantiFERON-TB Gold In-Tube test (QFG) (Cellestis, Carnegie, Australia) measures the level of soluble IFN-γ produced in whole blood by enzyme-linked immunosorbent assay (ELISA), and the T-SPOT.TB (Oxford Immunotec, Abingdon, UK) assay detects the number of IFN-γ -producing cells represented as spot-forming units (SFU). The gene discussed is IFNG; the disease is tuberculosis.