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Tuberculosis Interferon-Gamma Release Assay (TB-IGRA)

Published: July 27, 2026Updated: August 25, 2026

The TB-IGRA biomarker measures the release of interferon-gamma in response to Mycobacterium tuberculosis antigens, aiding in the diagnosis of latent or active tuberculosis infection.

Quick summary

TB-IGRA measures interferon-gamma levels to diagnose tuberculosis infection.

Medically reviewed by WellAlly Editorial TeamLast reviewed August 25, 2026Editorial policy

Key facts at a glance

Units
IU/mL
Clinical utility
diagnostic
Result kind
quantitative
FDA-cleared
QuantiFERON-TB Gold, T-SPOT.TB, LIAISON QuantiFERON
interpretation: {"text":"A result below 0.35 IU/mL suggests no significant interferon-gamma response to tuberculosis antigens, indicating a low likelihood of infection.","label":"Negative"}; {"text":"A result above 0.35 IU/mL indicates a significant interferon-gamma response, suggesting exposure to tuberculosis and the possibility of latent or active infection.","label":"Positive"}

TB-IGRA, or Tuberculosis Interferon-Gamma Release Assay, is a blood test that assesses the immune response to Mycobacterium tuberculosis antigens by measuring the release of interferon-gamma. This test is crucial for diagnosing latent tuberculosis infection (LTBI) and active tuberculosis disease.

The assay is particularly useful in differentiating tuberculosis from other pulmonary infections and in screening high-risk populations, such as healthcare workers and individuals with compromised immune systems. It is also beneficial in monitoring the effectiveness of tuberculosis treatment.

The reference range for TB-IGRA is typically 0–0.35 IU/mL. Results above this threshold are considered positive, indicating exposure to tuberculosis antigens and the possible presence of a tuberculosis infection.

Frequently asked questions

What is the difference between TB-IGRA and the tuberculin skin test (TST)?
TB-IGRA is a blood test that measures interferon-gamma release, while TST involves injecting tuberculin into the skin and measuring the resulting induration. TB-IGRA is less affected by prior BCG vaccination and is generally more specific.
Can TB-IGRA differentiate between latent and active tuberculosis?
No, TB-IGRA cannot differentiate between latent and active tuberculosis. It only indicates the presence of an immune response to tuberculosis antigens, and additional clinical evaluation is needed to determine the disease status.
  1. 1
    CDC - Interferon-Gamma Release Assays (IGRAs) - Blood Tests for TB InfectionSource
  2. 2
    WHO - Use of Tuberculosis Interferon-Gamma Release Assays (IGRAs)Source

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

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Medically reviewed by WellAlly Editorial Team Last reviewed August 25, 2026. · Read our editorial policy