What Is the QuantiFERON-TB Gold Test?
The QuantiFERON-TB Gold (QFT) test — also called an IGRA (Interferon-Gamma Release Assay) — is a blood test used to detect tuberculosis (TB) infection. It is the standard TB test required for most immigration medical exam applicants.
The test works by measuring your immune system's response to TB bacteria proteins. A small blood sample is drawn and sent to a certified laboratory. Results are typically available within 1–3 business days.
Blood test
A single blood draw — no injection of TB proteins into the skin.
1–3 day results
Results return from the laboratory within 1–3 business days.
No follow-up visit
Unlike the skin test, no return visit is needed to read results.
QuantiFERON Gold vs. TB Skin Test (TST)
The QuantiFERON-TB Gold test has largely replaced the older tuberculin skin test (TST/PPD) for immigration purposes. Here's how they compare:
| Feature | QuantiFERON-TB Gold (QFT) | TB Skin Test (TST) |
|---|---|---|
| Test type | Blood test | Intradermal injection |
| Return visit required | No | Yes (48–72 hours later) |
| BCG vaccine interference | Not affected | May cause false positive |
| Results timeline | 1–3 business days | Read at 48–72 hours |
| USCIS preference | Preferred/required | Limited use cases only |
Important for BCG-vaccinated applicants: If you received the BCG vaccine (common in many countries), the QuantiFERON-TB Gold test is significantly more accurate than the skin test. BCG vaccination does not cause a false positive on the QFT test.
What a Positive Result Means
Positive TB Test ≠ Denied Green Card
A positive QuantiFERON-TB Gold result means your immune system has been exposed to TB bacteria at some point in your life. It does not mean you have active TB disease, and it does not automatically make you inadmissible. The vast majority of applicants with positive TB tests successfully obtain their green cards.
A positive QFT result indicates TB infection — either latent (inactive) or active. The Civil Surgeon will conduct further evaluation to determine which type you have, as they are treated very differently for immigration purposes.
Latent TB vs. Active TB
Latent TB Infection (LTBI)
- TB bacteria present but inactive
- No symptoms, not contagious
- Positive QFT, normal chest X-ray
- NOT a ground of inadmissibility
- Treatment may be recommended but not required for immigration
- Most applicants with LTBI obtain green cards without issue
Active TB Disease
- TB bacteria active and multiplying
- Symptoms present (cough, fever, weight loss)
- Positive QFT, abnormal chest X-ray
- IS a ground of inadmissibility
- Treatment required before immigration can proceed
- Treatable — does not mean permanent denial
What Happens After a Positive Result
If your QuantiFERON-TB Gold test comes back positive, the Civil Surgeon will take the following steps:
Order a chest X-ray
A chest X-ray is required to evaluate for signs of active TB disease. This is typically done at a radiology facility.
Review symptoms and medical history
The Civil Surgeon will ask about TB symptoms (cough, fever, night sweats, weight loss) and any prior TB treatment.
Determine latent vs. active TB
Based on the chest X-ray results and clinical evaluation, the Civil Surgeon will classify the finding as latent or active TB.
Document findings on Form I-693
All TB-related findings are documented accurately on Form I-693 per USCIS Technical Instructions.
Advise on next steps
The Civil Surgeon will explain what the findings mean for your immigration case and what, if any, follow-up is required.
Chest X-Ray Requirements
A chest X-ray is required for all applicants 15 years of age and older who have a positive QuantiFERON-TB Gold test. It is also required for applicants with symptoms suggestive of TB disease, regardless of QFT result.
Who needs a chest X-ray
Applicants 15+ with a positive QFT result, or any applicant with TB symptoms regardless of age or QFT result.
Pregnancy exception
Pregnant applicants may defer the chest X-ray until after delivery. The Civil Surgeon will advise on the appropriate approach.
Where it's done
Chest X-rays are performed at a radiology facility. We can refer you to a convenient location near our Costa Mesa office.
What it shows
A chest X-ray can reveal signs of active TB disease, prior TB infection, or other pulmonary findings. A normal chest X-ray with a positive QFT typically indicates latent TB.
How TB Findings Affect Your Immigration Case
Reassurance: The overwhelming majority of applicants with positive TB tests have latent TB infection — which is not a ground of inadmissibility and does not prevent you from obtaining a green card.
Frequently Asked Questions
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Medical & Legal Disclaimer: The information on this page is provided for general educational purposes only and does not constitute medical or legal advice. TB testing requirements, USCIS policies, and immigration inadmissibility standards may change without notice. Always consult a USCIS-designated Civil Surgeon and a qualified immigration attorney for guidance specific to your individual case.