One of the remarkable advances in the diagnosis of tuberculosis (TB) in the last few decades has been the development and wide usage of interferon (IFN)-γ release assays (IGRAs). These assays quantify the in vitro release of IFN-γ from T-cells stimulated with Mycobacterium tuberculosis (M. tuberculosis) antigens. The innovation, together with their prevailing employment, facilitates the early identification of at-risk individuals allowing for early intervention treatment for latent TB infection, thereby preventing the spread of TB in health care settings and communities where the TB patients reside.
Two major IGRAs are widely utilized;one is QuantiFERON®-TB Gold In-Tube (QFT-GIT) (Cellestis, Victoria, Australia) and the other is T-SPOT.TB assay (Oxford Immunotec, Abingdon, United Kingdom). IGRAs, although not recommended for diagnosis of active TB in low- income countries, have been used to rule out latent TB infection especially for individuals who have received BCG or screening of health care workers.QFT-GIT simultaneously employs three M. tuberculosis antigens, ESAT-6, CFP-10, and TB7.7, to which cell- mediated immune responses are measured in a single tube.QFT- GIT replaces QuantiFERON®TB-Gold (QFT-G), which was the former generation of QuantiFERON applying two M. tuberculosis antigens with a separate reaction.