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The IGRA is a blood test used to see whether a person has been infected with Mycobacterium tuberculosis that is the bacteria causing TB Two IGRAs approved by FDA) are : QuantiFERON - TB Gold T-SPOT TB test Significance An IGRA test may be used to diagnose latent TB infection. It is not used to test for active TB disease. What is latent TB infection? Latent TB infection is when a person has the TB bacteria in their body but the immune system is stopping the infection causing disease. Latent TB infection causes no symptoms and cannot be passed on to other people. How do they work? IGRAs measure a person’s immune reactivity to M. tuberculosis. WBCs from most persons that have been infected with M. tuberculosis will release interferon-gamma (IFN-g) when mixed with antigens derived from M. tuberculosis. The antigens, testing methods, and interpretation criteria for IGRAs differ
