IFNG and tuberculosis: The In vitro production of gamma interferon is then detected by an Enzyme-Linked Immunosorbent Assay (QuantiFERON-TB Gold in-tube [QTF-GIT],) [13] or by the Enzyme-Linked Immunospot (T-SPOT TB) [14] IGRAs are more sensitive and more specific than the PPD test for the diagnosis of TB infection [15]–[18], and especially useful in BCG-vaccinated populations.