Interferon Gamma Release Assay Test for Mycobacterium Antigens

The Interferon Gamma Release Assay (IGRA) test is a blood test used to detect infection with Mycobacterium tuberculosis (TB) or other Mycobacterium species. Here's how it works:

Principle:

1. Blood samples are collected from the patient.
2. White blood cells (T-cells) are isolated from the blood.
3. T-cells are stimulated with Mycobacterium antigens (proteins) in a laboratory setting.
4. If the patient has been infected with Mycobacterium, their T-cells will recognize the antigens and release interferon-gamma (IFN-γ).
5. The amount of IFN-γ released is measured using an enzyme-linked immunosorbent assay (ELISA) or enzyme-linked immunospot (ELISpot) assay.

Interpretation:

1. Positive result: Indicates infection with Mycobacterium tuberculosis or other Mycobacterium species.
2. Negative result: Suggests no infection or previous BCG vaccination.
3. Indeterminate result: May occur due to technical issues or immune system disorders.

Advantages:

1. High sensitivity and specificity
2. Can detect latent TB infection
3. Less affected by BCG vaccination or environmental mycobacteria
4. Quick results (usually within 24 hours)

Limitations:

1. Does not distinguish between latent and active TB
2. May not detect early infection or recent conversion
3. Can be affected by immunosuppression or certain medical conditions

IGRA tests are widely used for TB screening, especially in low-prevalence settings or for individuals with increased risk of TB exposure.

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