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19001717 . Tuberculosis is a communicable disease caused by infection with M. tuberculosis (MTB) complex organisms, which typically spread to new hosts via airborne droplets from patients with respiratory tuberculosis disease.
. IGRA is an indirect test for M. tuberculosis infection that detects interferon-γ (IFN-γ) by ELISA technique.
. Individuals infected with MTB-complex organisms usually have
lymphocytes in their blood that recognize the organisms and secrete the cytokine IFN-γ. The detection and subsequent quantification of IFN-γ forms the basis of this test.
. A negative QFT-Plus result does not rule out M. tuberculosis infection or tuberculosis: false negatives may be due to the stage of infection (e.g., specimens obtained before the development of a cellular immune response), or to co-morbidities that affect immune function.
. A positive QFT-Plus result should not be the sole or definitive basis for determining M. tuberculosis infection. Further medical evaluation and diagnostic evaluation for active tuberculosis (e.g., AFB smear and culture, chest X-ray) are warranted.
