Mycobacterium tuberculosis-specific interferon-gamma release assay (serum/plasma)
This test measures your immune response to Mycobacterium tuberculosis, the bacterium responsible for tuberculosis. It helps determine if you’ve been exposed to TB bacteria, even if you don’t have active disease.
["Assesses past or latent TB exposure without symptoms."]
Key facts at a glance
- LOINC
- 71775-1
- Short code
- M TB IFN-g Pnl Bld
- Synonyms
- M TB IFN-g Pnl Bld
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Specimen volume
- 5 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 4–24 hours
- Order
- routine
What This Test Measures
The test detects the presence of specific antibodies or immune markers (interferon-gamma) produced by your white blood cells when exposed to TB bacteria. Unlike traditional TB tests, this one looks for your body’s active immune reaction rather than direct bacterial presence.
How the Test Works
Two types of samples are used: blood drawn from a vein (serum or plasma) and a small skin puncture (tuberculin test). The serum/plasma IGRA specifically measures interferon-gamma released by your immune cells when stimulated with TB-specific proteins, indicating exposure.
When You Might Need This Test
Doctors may recommend this test if you’ve had recent contact with someone who has active TB, if you’re immunocompromised, or if you live in areas with higher TB rates. It’s also used for monitoring latent TB infection in high-risk groups.
What to Expect Before the Test
No special preparation is needed. You may have a blood draw (like for other tests) or a small skin test (tuberculin test) at a separate visit. If you’re on certain medications (like steroids), let your doctor know before testing.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
A positive result suggests past exposure to TB bacteria, which may require further evaluation for latent infection. A negative result means your immune system hasn’t recognized TB proteins, but it doesn’t rule out possible exposure. This test is critical for identifying latent TB in high-risk individuals before it progresses to active disease.
Short name
TB IGRA (Serum/Plasma)
Frequently asked questions
Can this test confirm active TB?
How long does it take to get results?
Is this test covered by insurance?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
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.
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