What it means
White blood cells from the sample are mixed with proteins from the TB bacterium. If the person has been infected, their cells release a substance called interferon-gamma, which the test measures. It needs only one visit, and a past BCG vaccine does not cause a false positive. Like the skin test, it cannot tell latent infection from active tuberculosistoo-ber-kyoo-LOH-sisAn infection caused by the bacterium Mycobacterium tuberculosis, which most often attacks the lungs.tubercul/o small swelling-osis abnormal conditionFull entry .
For the nurse
A positive result needs a chest x-ray and an assessment for symptoms of active disease. Note that no return visit is needed to read it, unlike the skin test.
At a glance
| Normal range | Negative |
|---|---|
| Also written | interferon gamma release assay, IGRA, QuantiFERON, QuantiFERON-TB Gold, T-SPOT.TB |
Related terms
tuberculosis
An infection caused by the bacterium Mycobacterium tuberculosis, which most often attacks the lungs.