Tuberculosis (TB) Blood Test (QuantiFERON)
The QuantiFERON TB blood test is a modern alternative to the tuberculin skin test that measures immune response to detect latent or active tuberculosis infection.
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Lab testing services linked from this site are not available to residents of Alaska, Arizona, or Hawaii, unless otherwise noted on the lab's own website.
This publication is not intended to solicit the purchase of laboratory testing from any individual consumer.
What this test measures
The QuantiFERON-TB Gold Plus is an interferon-gamma release assay (IGRA) that detects immune responses to Mycobacterium tuberculosis, the bacterium that causes tuberculosis. Rather than looking for antibodies, this test measures whether specialized immune cells (T cells) react to TB-specific proteins. A blood sample is incubated with peptide antigens derived from two M. tuberculosis proteins (ESAT-6 and CFP-10), and if T cells have been previously sensitized by TB exposure, they release interferon-gamma, a signaling molecule that the test quantifies.
A key advantage of this test over the traditional tuberculin skin test (TST) is its specificity. The ESAT-6 and CFP-10 proteins are absent from all BCG vaccine strains and from most nontuberculous mycobacteria, which means the test produces far fewer false positives in BCG-vaccinated individuals. However, a positive result cannot distinguish between active TB disease (in which the bacteria are currently causing illness) and latent TB infection (in which the bacteria are present but dormant). Additional evaluation, including chest imaging and clinical assessment, is needed to make that distinction.
Who should consider this test
You might consider this test if you are experiencing any of the following:
- Individuals who have been exposed to someone with active tuberculosis and need to determine if they have been infected with the TB bacteria.
- Healthcare workers, first responders, and those in high-risk occupations who require regular tuberculosis screening as part of their employment requirements.
- People who have received the BCG vaccine and need tuberculosis testing, as the QuantiFERON test is not affected by prior BCG vaccination unlike the traditional skin test.
- Patients who are unable to return for tuberculin skin test reading appointments, as the QuantiFERON requires only one laboratory visit for blood collection.
- Those who are immunocompromised or have conditions that may affect their ability to mount an immune response, where more precise testing may be beneficial.
- Individuals traveling to or immigrating from countries with high tuberculosis rates who need documentation of their TB infection status.
- People with symptoms suggestive of tuberculosis infection or disease who need evaluation as part of their diagnostic workup.
What to expect
Preparation
No fasting or special preparation is required. Individuals should inform their healthcare provider of any medications they are taking, particularly immunosuppressive drugs that might affect immune function.
Sample Type
A healthcare professional will collect a blood sample from a vein in the arm using a standard needle. The blood is collected into special tubes containing specific antigens that will stimulate an immune response if TB infection is present.
Collection
The blood draw typically takes just a few minutes at the laboratory location. The special collection tubes may take slightly longer to fill than standard blood collection tubes due to their unique design.
Turnaround
Test results are typically available within 2-5 business days after the laboratory receives the specimen.
Understanding your results
Results are reported as positive, negative, or indeterminate based on the quantity of interferon-gamma released in response to TB-specific antigens. A positive result indicates that M. tuberculosis infection is likely, meaning the immune system has been exposed to the bacterium, but does not specify whether the infection is active or latent. A negative result indicates that TB infection is unlikely, though no test is 100% sensitive and false negatives can occur, particularly in immunocompromised individuals. An indeterminate result means the test could not be interpreted reliably and may need to be repeated. Healthcare providers use the result alongside chest radiography, symptom assessment, and exposure history to determine the appropriate clinical response.
| Population | Reference Range | Notes |
|---|---|---|
| Adults and children | Negative: < 0.35 IU/mL | Standard cutoff for negative results |
| Adults and children | Positive: ≥ 0.35 IU/mL | Indicates likely TB infection |
| Adults and children | Borderline: 0.20-0.99 IU/mL | May require repeat testing for confirmation |
Reference ranges may vary by laboratory and individual factors. Results should be interpreted by a healthcare provider in the context of your overall health.
What does a “Low” result mean?
A negative result does not preclude the possibility of Mycobacterium tuberculosis infection or tuberculosis disease, as false negative results can occur due to the stage of infection, conditions that affect immune function, or improper specimen handling. Indeterminate results are rare (0% to 2.3% of all results) and may be caused by a compromised immune system or inappropriate specimen handling. An indeterminate result suggests possible preanalytic error or individual patient-related factors.
What does a “High” result mean?
A positive QuantiFERON-TB Gold Plus result indicates that Mycobacterium tuberculosis infection is very likely. However, the test cannot distinguish between active tuberculosis disease and latent tuberculosis infection. Positive results should not be the sole basis for determining TB infection and should be followed by further medical evaluation for active tuberculosis disease. False-positive results may occur due to improper specimen processing, prior infection with certain other mycobacteria, or biological variability.
Privacy & confidentiality
All QuantiFERON tuberculosis test results are kept strictly confidential and protected under HIPAA regulations. Results are not automatically shared with your personal physician, added to your medical records, or reported to insurance companies unless you specifically request it. No doctor visit is required to order this test.
Frequently asked questions
Related tests
Last reviewed: April 2026
CPT Code: 86480
This test may not be available in: NY, NJ, RI
This page is for informational purposes only and does not constitute medical advice. Always consult with a healthcare provider regarding any health concerns. LevelPanel does not diagnose, treat, or prescribe.
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LevelPanel has no business or affiliate relationship with Quest or LabCorp. These links are provided as a public service.
Lab testing services linked from this site are not available to residents of Alaska, Arizona, or Hawaii, unless otherwise noted on the lab's own website.
This publication is not intended to solicit the purchase of laboratory testing from any individual consumer.
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