The blood tests used to detect Tuberculosis (TB) infection are commonly known as interferon-gamma release assays, or IGRAs.
Understanding TB Blood Tests (IGRAs)
TB blood tests, also officially termed interferon-gamma release assays (IGRAs), serve as a critical diagnostic tool to determine if an individual has been infected with TB germs. These sophisticated tests analyze your immune system's response to specific components of the TB bacteria.
According to health guidelines, these tests operate by:
- Utilizing a small blood sample taken from the patient.
- Measuring the reaction of your immune system when a minute quantity of your blood is mixed with specific TB proteins.
This measurement helps healthcare professionals ascertain if your body has encountered and reacted to Mycobacterium tuberculosis, the bacterium responsible for TB.
How Interferon-Gamma Release Assays Work
When a person is infected with TB, their immune cells develop a memory of the bacteria. IGRAs are designed to detect this immune memory.
Here’s a breakdown of the process:
- Blood Sample Collection: A healthcare professional draws a small amount of blood, typically from a vein in your arm.
- Incubation with TB Antigens: The collected blood sample is then mixed with synthetic proteins that are highly specific to the Mycobacterium tuberculosis bacteria.
- Immune Response Measurement: If the individual has been exposed to TB in the past, their T-lymphocytes (a type of white blood cell) will recognize these TB proteins. In response, these T-cells release a cytokine called interferon-gamma (IFN-γ).
- Result Interpretation: The test then quantifies the amount of IFN-γ produced. A significant presence of IFN-γ indicates a positive result, suggesting an infection with TB germs.
IGRAs offer several advantages over traditional tests, such as requiring only a single blood draw and not being influenced by prior BCG (Bacille Calmette-Guérin) vaccination, which can cause false positives in tuberculin skin tests. For more comprehensive information on TB, its symptoms, and preventive measures, you can consult reputable sources like the Centers for Disease Control and Prevention.
