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Mtbifngtcellsbckgrdcorbldacnc

Published: August 9, 2026Updated: August 17, 2026

A blood test that measures how your immune cells respond to tuberculosis bacteria to determine if you have a TB infection.

Quick summary

{"Detects TB infection by measuring immune response to TB proteins","Requires a small blood sample drawn from your arm","Cannot distinguish between latent (dormant) and active TB disease","Results are typically available within 1-3 days","Previous TB vaccination may affect test results"}

Medically reviewed by WellAlly Editorial TeamLast reviewed August 17, 2026Editorial policy

Key facts at a glance

LOINC
96754-7
Short code
QFT-TB IGRA
Synonyms
M TB IFN-g T-cells bckgrd cor Bld-aCnc
Category
cardiac
Sample
whole-blood
Container
Lithium heparin tube (green top) - specialized QuantiFERON-TB Gold Plus collection tubes
Units
N/A
Ref low
25
Ref high
200
Critical range
— – 10000 N/A
Fasting
false
Population
adult
Sex
all
Age range
≥ 0 years
Method
Interferon Gamma Release Assay (IGRA) - Enzyme-linked immunosorbent assay (ELISA)
CPT
86480
SNOMED
709510006
Specimen volume
1 mL whole blood per collection tube (4 tubes total: nil, TB1, TB2, mitogen)
Stability
Process within 8-30 hours of collection when stored at room temperature (22°C ± 5°C). Do not refrigerate or freeze whole blood. Incubate within 16 hours of collection.
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
24–72 hours
Order
routine

What is this test?

This test, also known as an Interferon Gamma Release Assay (IGRA), measures the amount of interferon-gamma (a type of protein released by immune cells) in your blood after your T-cells are exposed to specific antigens from Mycobacterium tuberculosis (the bacteria that causes TB). It helps determine if your body has been infected with TB.

Why do I need this test?

Your healthcare provider may order this test if you have symptoms of active TB (such as persistent cough, fever, night sweats, or weight loss), if you have been exposed to someone with TB, or if you need TB screening for work, school, or travel purposes. It is also used for people with weakened immune systems who are at higher risk for TB.

How is the test performed?

A healthcare professional will draw a small amount of blood from a vein in your arm. The blood sample is then sent to a laboratory where it is mixed with TB antigens and incubated. The lab measures the amount of interferon-gamma released by your T-cells in response to these antigens.

What do the results mean?

Results are reported as positive, negative, or indeterminate. A positive result means your immune system has responded to TB antigens, indicating TB infection (either latent or active). A negative result suggests no TB infection, but it cannot completely rule out early or very recent infections. An indeterminate result means the test could not provide a clear answer, and repeat testing may be needed.

Reference range

NCBI: CK 25-200 U/LN/A

Specimen: whole-blood

No fasting required. No special preparation needed. Inform laboratory of immunosuppressive medications, recent infections, or prior TB testing. Collect specimen prior to tuberculosis skin testing or at least 48 hours after.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Frequently asked questions

Does this test tell me if I have active TB disease?
No, this test cannot distinguish between latent TB infection and active TB disease. If your test is positive, your healthcare provider will perform additional tests (such as chest X-ray, sputum culture, or PCR) to determine if you have active TB disease that requires treatment.
Will the TB vaccine (BCG) affect my test results?
Unlike the traditional tuberculin skin test (TB skin test), the BCG vaccine generally does not cause a positive result on this gamma interferon test. This is because the test uses TB-specific antigens that are not present in the BCG vaccine.
Do I need to fast before this test?
No, fasting is not required for this test. You can eat and drink normally before having your blood drawn.
How long does it take to get results?
Results are typically available within 1-3 days, though this may vary depending on the laboratory.
Can this test detect all types of TB?
This test detects infection with Mycobacterium tuberculosis, the bacteria that causes TB disease. It does not detect other mycobacterial infections such as Mycobacterium avium complex.
  1. 1
    CDC - Interferon Gamma Release Assays (IGRAs)Source
  2. 2
    Mayo Clinic - Interferon Gamma Release AssaySource

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 17, 2026. · Read our editorial policy