Quantiferon TB Gold Plus 1 Tube Biomarker Testing
It checks for TB infection by measuring interferon‑gamma response in your blood, with easy ordering and clear results through Vitals Vault/Quest.
With Vitals Vault, you have access to a comprehensive range of biomarker tests.
Quantiferon TB Gold Plus 1 Tube (often written as QuantiFERON-TB Gold Plus or QFT-Plus) is a blood test used to screen for tuberculosis (TB) infection. It does not look for the TB bacteria directly. Instead, it measures how your immune system reacts to TB-specific proteins.
This test is commonly used for work or school clearance, healthcare employment, immigration-related screening, and for people who have had a possible exposure. It is also used when a skin test (TST/PPD) is inconvenient or hard to interpret.
Your result is usually reported as Negative, Positive, or Indeterminate, along with several numeric values that help explain why the lab called it that. Those details matter, especially if you are immunocompromised or if your risk of exposure is low.
Do I need a Quantiferon TB Gold Plus 1 Tube test?
You may need this test if you are being screened for TB infection because of a job requirement (such as healthcare or childcare), school enrollment, travel or immigration paperwork, or a planned medication that can weaken your immune system. It is also a common next step after a known exposure to someone with active TB.
This test can be a good fit if you have received the BCG vaccine in the past. BCG can cause false-positive TB skin tests, while an IGRA blood test like QFT-Plus is designed to be more specific to TB infection.
If you currently have symptoms that could fit active TB—such as a persistent cough, coughing up blood, fevers, night sweats, unexplained weight loss, or chest pain—blood screening alone is not enough. You typically need prompt clinical evaluation and additional testing (like a chest X-ray and sputum testing).
Testing is most useful when it is interpreted alongside your exposure risk, symptoms, and medical history. A lab result supports clinician-directed care; it is not a stand-alone diagnosis of active TB disease.
This is a CLIA laboratory test (an interferon-gamma release assay, IGRA) used for TB infection screening; results must be interpreted with your clinical risk and are not a stand-alone diagnosis of active TB disease.
Lab testing
Order Quantiferon TB Gold Plus 1 Tube through Vitals Vault when you need documentation or a blood-based TB screen.
Schedule online, results typically within about a week
Clear reporting and optional clinician context
HSA/FSA eligible where applicable
Get this test with Vitals Vault
With Vitals Vault, you can order Quantiferon TB Gold Plus 1 Tube for screening when you need documentation or when you and your clinician want a blood-based alternative to a skin test. You choose a nearby draw location, complete a standard blood draw, and then review your results when they are ready.
Because TB screening decisions depend on your risk level and immune status, it helps to have a clear explanation of what “positive,” “negative,” and “indeterminate” mean in your specific situation. PocketMD can help you understand the report language, what follow-up questions to ask, and when retesting is reasonable.
If your result is positive, the next step is usually evaluation for active TB (often with imaging and sometimes sputum tests), plus a discussion about treatment for latent TB infection when appropriate. If your result is indeterminate, you may need a repeat test or a different testing approach depending on why the control values were abnormal.
- Order online and schedule a local blood draw
- PocketMD support for understanding your report and next steps
- Results designed to be easy to share with your clinician or employer
Key benefits of Quantiferon TB Gold Plus 1 Tube testing
- Screens for TB infection using a blood-based immune response rather than a skin reaction.
- Helps reduce false positives related to prior BCG vaccination compared with a TB skin test.
- Provides built-in controls (Nil and Mitogen) that help explain unclear results.
- Supports occupational, school, and clearance documentation with a standardized lab report.
- Can be used when returning for a skin test reading is impractical.
- Helps guide whether you need follow-up evaluation for active TB versus latent TB management.
- Makes it easier to track and discuss results with PocketMD and your clinician when retesting is needed.
What is Quantiferon TB Gold Plus 1 Tube?
Quantiferon TB Gold Plus is an interferon-gamma release assay (IGRA). After your blood is collected, your immune cells are exposed in the lab to TB-specific antigens (proteins). If you have been infected with Mycobacterium tuberculosis at some point, certain white blood cells (T cells) may release interferon-gamma (IFN-γ) in response.
The “Plus” version uses two antigen tubes designed to stimulate different T-cell responses (often described as TB1 and TB2). The lab compares the interferon-gamma response in those tubes to a baseline “Nil” tube (background) and checks an additional “Mitogen” tube (a positive control) to confirm your immune cells can respond at all.
A key point: this test is designed to detect TB infection, but it cannot reliably tell you whether the infection is latent (sleeping) or active (contagious disease). That distinction depends on symptoms, imaging, and sometimes microbiology testing.
IGRA vs TB skin test (TST/PPD)
A TB skin test measures swelling in your skin after an injection and requires a return visit for reading. Quantiferon is a blood test that does not require a second visit for interpretation, and it is generally less affected by BCG vaccination. Either test can be appropriate depending on your setting, age, and risk profile.
Why the control tubes matter
The Nil tube helps subtract background interferon-gamma that can be present for reasons unrelated to TB. The Mitogen tube checks whether your immune system can mount a response; if it is low, the lab may call the result indeterminate because the test cannot confidently rule TB in or out.
What do my Quantiferon TB Gold Plus 1 Tube results mean?
Low / negative result
A negative result usually means the test did not detect an immune response consistent with TB infection. If you have no symptoms and your exposure risk is low, this is generally reassuring. If you were tested very soon after a known exposure, your immune response may not be detectable yet; many clinicians consider retesting about 8–10 weeks after the last exposure if risk is meaningful. A negative result does not rule out active TB in someone with strong symptoms or significant immune suppression.
In-range controls with a clear result
The most interpretable reports have a low Nil value (low background) and a strong Mitogen response (your immune cells reacted appropriately to the control). With those controls in range, a Negative or Positive call is more dependable. If you are using the test for clearance documentation, this is typically what schools and employers want to see. Keep a copy of the full report because it includes the control values that explain the lab’s call.
High / positive result
A positive result means your immune system released interferon-gamma in response to TB-specific antigens, which is consistent with TB infection (often latent TB infection). It does not prove you have active, contagious TB disease, and it does not identify when the infection occurred. Next steps commonly include a symptom review and chest imaging to look for active disease, and then a discussion about whether treatment for latent TB is recommended based on your risk factors. If your risk of exposure is very low, your clinician may also consider the possibility of a false positive and whether repeat testing is appropriate.
Factors that influence Quantiferon results
Immune suppression can lead to indeterminate or falsely negative results, including from advanced HIV, certain cancers, organ transplant medications, high-dose steroids, or some biologic therapies. Very recent TB exposure can test negative before your immune system has time to respond. Pre-analytical issues—such as delayed incubation, inadequate mixing of tubes, or improper handling—can also produce indeterminate results. Age extremes and serious acute illness can affect the Mitogen control, which is one reason your clinician may recommend repeating the test when you are clinically stable.
What’s included
- Mitogen-Nil
- Nil
- Quantiferon(R)-Tb Gold Plus, 1 Tube
- Tb1-Nil
- Tb2-Nil
Frequently Asked Questions
Is Quantiferon TB Gold Plus a test for active TB?
It is a test for TB infection, not a stand-alone test for active TB disease. If you have symptoms or an abnormal chest X-ray, you typically need additional evaluation (often imaging and sometimes sputum testing) to assess for active TB.
What does an indeterminate Quantiferon result mean?
Indeterminate means the test controls did not behave as expected, so the lab cannot reliably call the result positive or negative. Common reasons include a low Mitogen response (your immune cells did not respond well), a high Nil value (high background), or specimen handling issues. Your clinician may recommend repeating the test or using a different approach based on your risk.
Do I need to fast for a Quantiferon TB Gold Plus test?
Fasting is not typically required. You can usually eat and drink normally unless your blood draw includes other tests that require fasting.
How soon after TB exposure should I get tested?
If you test too early, the result can be negative even if infection later becomes detectable. Many clinicians consider testing promptly to establish a baseline and then retesting about 8–10 weeks after the last exposure if the exposure was significant.
Can the BCG vaccine make Quantiferon positive?
Quantiferon is designed to use TB-specific antigens that are not part of the BCG vaccine, so BCG is much less likely to cause a false positive compared with a TB skin test. No test is perfect, so your exposure risk still matters when interpreting a result.
If my Quantiferon is positive, do I need treatment?
A positive test often leads to evaluation for active TB and then a discussion about treatment for latent TB infection. Whether treatment is recommended depends on your risk factors (such as recent exposure, immune suppression, or certain medical conditions) and your clinician’s assessment.
Why are there TB1 and TB2 values on my report?
TB1 and TB2 are two antigen responses used in the QFT-Plus method. They provide more detail about interferon-gamma release in response to TB antigens, while the Nil and Mitogen controls help confirm the result is interpretable.