<prompt> The test is used for:TuberculosisSyphilisSarcoidosisHepatitis B  <response>: The principles of interferon-gamma release assays IGRAs. A sample of either A purified T cells T- SPOT TB test or B whole blood QuantiFERONTB Gold test is incubated in the presence of antigens specific to Mycobacterium tuberculosis MTB. The release of interferon-gamma IFN-γ by the cells is measured by enzyme-linked immunosorbent assay ELISA. ELISPOT enzyme-linked immunosorbent spot assay.Ref: Davidson Ed 22nd Pg 695 