IFNG and tuberculosis: Although there are well-established methods to diagnose TB, they have well-known drawbacks such as insufficient sensitivity (sputum smear), long (4-to-8-week) turnaround time to results (culture) (3), and inability to differentiate LTBI from TB (tuberculin skin test [TST], interferon gamma [IFN-γ] release assay [IGRA]) (6, 7).