The test is used for:

The principles of interferon-gamma release assays (IGRAs). A sample of either (A) purified T cells (T- SPOT TB test) or (B) whole blood (QuantiFERON–TB 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