Mycobacterium tuberculosis QuantiFERON-TB Gold Plus (IFN-γ release assay)
This blood test measures the body’s 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.
["This test checks for past or recent TB exposure without symptoms."]
Key facts at a glance
- LOINC
- 72276-9
- Short code
- MTB gyrA fluoroquin res mut Islt/Spm Ql
- Synonyms
- MTB gyrA fluoroquin res mut Islt/Spm Ql
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Ref low
- 0.8
- Ref high
- 1.2
- Critical range
- — – 5 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- molgen
- CPT
- 85610
- SNOMED
- 396252006
- 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
Why This Test Is Done
Your doctor may recommend this test if you have risk factors for TB, such as living or traveling in areas with higher TB rates, having certain medical conditions, or being in close contact with someone diagnosed with TB. It’s also used to screen people before certain procedures (like surgery) or before starting treatments that weaken the immune system.
How the Test Works
The test uses a small blood sample to detect specific immune cells that release interferon-gamma (IFN-γ) when exposed to TB-specific proteins. This response indicates a past or current immune reaction to TB, but not necessarily active disease.
What to Expect Before the Test
No special preparation is needed. You may have a slight bruise or soreness at the injection site, but this is normal. Avoid alcohol before the test, as it may affect blood clotting.
What the Results Mean
A positive result suggests a past exposure to TB bacteria. A negative result means no detectable immune response, which may indicate no exposure or a very recent one. A weak or borderline result may need further testing.
Reference range
INR: 0.8-1.2 (warfarin: 2.0-3.0)N/A
Inform your healthcare provider if you are taking blood thinners. No special preparation required.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Clinical Significance
Short name
TB IGRA (Interferon-Gamma Release Assay)
Frequently asked questions
What does a positive result mean?
What does a negative result mean?
How often should I get this test?
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