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Tuberculosis Interferon-Gamma Release Assay (IGRA) for Blood

Published: August 9, 2026Updated: August 16, 2026

This blood test measures your immune response to tuberculosis (TB) bacteria by detecting interferon-gamma released when your white blood cells encounter specific TB proteins. It helps determine if you’ve been exposed to TB, even if you don’t have active symptoms.

Quick summary

["Assesses TB exposure without requiring active infection symptoms."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
82510-9
Short code
M bovis tuberc stim IFN-g Bld-Imp
Synonyms
M bovis tuberc stim IFN-g Bld-Imp
Category
chemistry
Sample
whole-blood
Container
Lavender-top (EDTA)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Specimen volume
3 mL
Stability
Room temperature: 4h, Refrigerated: 24h
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
4–24 hours
Order
routine

How the Test Works

Your blood is drawn and mixed with two sets of TB-specific proteins. If your immune system has encountered TB bacteria, your white blood cells will release interferon-gamma. This reaction is captured and measured to confirm exposure.

What to Expect Before the Test

No special preparation is needed. Wear comfortable clothing for easy blood draw. You may feel slight discomfort at the needle site, but it’s usually over quickly. Avoid alcohol or strenuous activity 24 hours before the test.

Common Questions About the Test

This test is not for diagnosing active TB. It only checks for past or recent exposure. If you have symptoms like coughing, fever, or chest pain, see your doctor immediately for further evaluation.

Who Might Need This Test

Healthcare providers may recommend this test for people at higher risk of TB exposure, such as travelers to high-risk countries, individuals in close contact with TB patients, or those with weakened immune systems.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

T-Spot or QuantiFERON-TB Gold In-Tube

Frequently asked questions

Why was I asked to take this test?
Your doctor may have recommended this test to assess your risk of TB exposure, especially if you’ve traveled to regions with higher TB rates, live with someone who has TB, or have a condition that weakens your immune system.
What do my results mean?
A positive result suggests you’ve been exposed to TB bacteria, but it doesn’t confirm active disease. A negative result means you likely haven’t been exposed recently. Follow-up testing or evaluation may be needed based on your symptoms and risk factors.
Can I get TB from this test?
No, this test does not expose you to TB bacteria. It uses harmless proteins to measure your immune response, ensuring your safety throughout the process.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

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.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy