Tb Platinum Igra, Blood

Function

The Interferon-Gamma Release Assay (IGRA) is a modern blood test used to detect infection by Mycobacterium tuberculosis. Unlike the traditional skin test (Mantoux), IGRA measures the immune system's response to specific TB proteins. When white blood cells from an infected person are mixed with these proteins, they release a cytokine called Interferon-Gamma (IFN-g). This test specifically targets proteins that are not present in the BCG vaccine, reducing false positives.

Why it is Ordered

This test is ordered for individuals who have been exposed to someone with active TB, healthcare workers undergoing routine screening, or individuals beginning immunosuppressive therapy (like TNF-inhibitors). It is the preferred method for TB screening in individuals who have received the BCG vaccine, as it provides a more specific result than the skin test.

Associated Conditions

• Latent TB Infection (LTBI): The person is infected but not contagious and has no symptoms.
• Active TB Disease: The person is symptomatic and can spread the bacteria to others.
• Extrapulmonary TB: Infection outside the lungs (e.g., kidneys, spine, or brain).

Limitations

It is critical to note that the IGRA test cannot distinguish between latent and active TB. Diagnosis of active TB requires clinical symptoms, chest X-rays, and sputum cultures.