Interferon-Gamma Release Assays (IGRAs) – Blood Tests for TB Infection

What are they?

Interferon-Gamma Release Assays (IGRAs) are whole-blood tests that can aid in diagnosing Mycobacterium tuberculosis infection

How do they work?

IGRAs measure a person’s immune reactivity to M. tuberculosis. White blood cells from most persons that have been infected with M. tuberculosis will release interferon-gamma (IFN-g) when mixed with antigens (substances that can produce an immune response) derived from M. tuberculosis.

To conduct the tests, fresh blood samples are mixed with antigens and controls. The antigens, testing methods, and interpretation criteria for IGRAs differ

What are the advantages of IGRAs?

- Requires a single patient visit to conduct the test.

- Results can be available within 24 hours.

- Does not boost responses measured by subsequent tests.

- Prior BCG (bacille Calmette-Guérin) vaccination does not cause a false-positive IGRA test result.