In vitro gamma interferon tests for the detection of tuberculosis infection

The QuantiFERON-TB Gold (QFT-G) is a new FDA approved test for diagnosing Mycobacterium tuberculosis infection. This test detects the release of interferon-gamma (IFN gamma) in whole blood from sensitized persons when it is incubated with mixtures of synthetic peptides representing 2 proteins present in M. tuberculosis: early secretory antigenic target-6 (ESAT-6) and culture filtrate protein-10 (CFP-10). These antigens have greater specificity than tests using purified protein derivative (PPD) as the tuberculosis antigen. The CDC recommends that QFT-G may be used in all circumstances in which the TB skin test is currently used, including contact investigations, evaluation of recent immigrants, and sequential-testing surveillance programs for infection control (e.g., those for healthcare workers). Advantages of the QFT-G include: no false-positive reactions from previous BCG vaccination; no cross-reactivity with non-tuberculous mycobacterium infections; and, better detection of active tuberculosis.