The QuantiFERON TB Gold test — also called QFT or IGRA (interferon-gamma release assay) — is a modern blood test used to detect tuberculosis infection. It’s replacing the traditional TB skin test (PPD) in many clinical and occupational settings because it requires only one visit, has no subjective reading, and works accurately in people who’ve received the BCG vaccine.
CityHealth San Leandro offers the QuantiFERON TB Gold test for healthcare workers, new employees, school requirements, and anyone else who needs TB clearance. Here’s everything you need to know before your visit.
QuantiFERON TB Gold Test vs. TB Skin Test (PPD): What’s the Difference?
Both tests detect tuberculosis infection, but they work differently and each has advantages in certain situations. Here’s a side-by-side comparison:
TB Skin Test (TST / Mantoux / PPD)
- A small amount of tuberculin is injected under the skin on the forearm
- You must return 48–72 hours later for a trained clinician to read the result
- The reading is based on the size of any skin reaction — which can be affected by the reader’s technique
- Can show a false positive in people who received the BCG vaccine (common outside the United States)
- Requires two visits
QuantiFERON TB Gold Test (QFT / IGRA)
- A single blood draw — no injection under the skin
- One visit only — no return trip for a reading
- Results are measured in a lab — no subjective reading by a clinician
- Not affected by BCG vaccination — far fewer false positives
- Preferred for people who are unlikely to return for a second visit
- Preferred for immunocompromised patients and BCG-vaccinated individuals
The CDC and most major health systems now recognize QuantiFERON as equivalent or superior to the skin test for most populations.
Need a QuantiFERON TB Gold test? CityHealth San Leandro offers single-visit TB blood testing — no return trip required.
Book Your TB Test Appointment
Who Needs the QuantiFERON TB Gold Test?
The QFT is recommended or required for specific groups. Here are the most common situations:
Healthcare Workers
Hospitals, clinics, and long-term care facilities require TB testing for all new employees and often on an annual basis. Because healthcare workers are at higher risk of TB exposure, routine screening is essential. The QuantiFERON test is preferred in many healthcare settings because it eliminates the need for a return visit and reduces false positives.
BCG-Vaccinated Individuals
The BCG (Bacillus Calmette-Guérin) vaccine is routinely administered in many countries outside the United States, including much of Asia, Latin America, Africa, and Eastern Europe. BCG vaccination causes a reaction to the TB skin test that can’t be distinguished from a true positive for TB infection. The QuantiFERON TB Gold test is not affected by BCG vaccination — making it the strongly preferred test for anyone who received BCG as a child.
Immunocompromised Patients
People with HIV, those on immunosuppressive medications (such as biologics for rheumatoid arthritis or Crohn’s disease), and organ transplant recipients may have impaired skin reactions that make the TST unreliable. Blood-based IGRA testing is often more accurate for this group.
People Unlikely to Return for a Second Visit
If returning 48–72 hours later for a skin test reading is a barrier — due to work schedules, transportation, or distance — the QuantiFERON test eliminates that problem entirely.
School and Program Requirements
Some schools, nursing programs, dental programs, and universities specify QuantiFERON (IGRA) rather than a skin test for TB clearance.
Immigration and Travel
Some immigration medical evaluations and international travel requirements call for IGRA testing. Check with your immigration attorney or civil surgeon about whether QuantiFERON satisfies your specific requirement.
How the QuantiFERON Test Works
The science behind the QuantiFERON test is elegant. Here’s the simplified version:
When someone is infected with Mycobacterium tuberculosis (the bacteria that causes TB), their immune system develops a memory response. White blood cells called T-cells become sensitized to TB-specific proteins.
The QuantiFERON test mixes your blood with TB-specific antigens in a lab. If your T-cells have been sensitized to TB (meaning you’ve been infected at some point), they release a protein called interferon-gamma. The lab measures how much interferon-gamma is released:
- High levels: Positive result — TB infection detected (latent or active)
- Low or no interferon-gamma: Negative result — no evidence of TB infection
Crucially, the BCG vaccine does not cause T-cell sensitization to the same antigens used in the test. That’s why BCG doesn’t cause false positives on QuantiFERON.
What to Expect at CityHealth During Your QuantiFERON Visit
- Check in — Walk in or book online. Bring any documentation from your employer, school, or institution.
- Brief intake — The nurse will confirm which TB test you need and document your clinical history.
- Blood draw — A quick venipuncture from your arm. Multiple tubes of blood are drawn and incubated with TB antigens in the lab.
- Lab processing — Your blood sample is sent to a certified reference lab for processing.
- Results — Results are typically available in 2–5 business days. We’ll notify you and provide official documentation.
You don’t need to fast. You don’t need a referral. Come in during any of our hours and we’ll take care of the rest.
QuantiFERON TB Gold Test Results: What They Mean
A positive QuantiFERON result does not mean you have active tuberculosis disease. It means your immune system has been exposed to TB bacteria at some point — what’s called latent TB infection (LTBI). Most people with LTBI never develop TB disease, but treatment is often recommended to prevent the latent infection from becoming active.
A negative result means there’s no evidence of TB infection.
An indeterminate result means the test couldn’t be conclusively interpreted — this can happen in immunocompromised patients or due to technical issues. A repeat test may be recommended.
If your result is positive, your provider will discuss next steps, which may include a chest X-ray to rule out active TB disease and a referral to a TB specialist or public health clinic for LTBI treatment.
QuantiFERON Test Cost and Insurance
Costs depend on your insurance and the reason for testing:
- With insurance: Often covered as occupational health, preventive screening, or pre-employment testing. Confirm with your insurer.
- Without insurance (cash pay): QuantiFERON testing typically runs $60–$120. Ask at the time of your visit — we’ll give you an upfront estimate.
For more information on TB testing costs, see our dedicated post: How Much Does a TB Test Cost?. For general TB test information including the traditional skin test, see our TB test page.
Book Same-Day Care at CityHealth
CityHealth San Leandro — open 7 days a week. Walk-ins welcome, most insurance accepted. On-site lab and X-ray.
QuantiFERON vs. Other IGRA Tests
QuantiFERON-TB Gold Plus (QFT-Plus) is the most widely used IGRA test. There’s also a test called T-SPOT.TB, which uses a slightly different method but detects the same interferon-gamma response. Both are CDC-approved alternatives to the TB skin test. CityHealth uses the QuantiFERON platform — if your employer or institution specifically requires T-SPOT, let us know and we can discuss options.
According to the CDC’s IGRA testing guidance, interferon-gamma release assays are preferred over TST in most circumstances, particularly for BCG-vaccinated individuals and those unlikely to complete the two-visit skin test process.
How Accurate Is the QuantiFERON TB Gold Test?
The QuantiFERON TB Gold Plus test has a sensitivity of approximately 89–94% for detecting latent TB infection, according to studies published in the Journal of Clinical Microbiology. Its specificity exceeds 95% in populations not previously vaccinated with BCG.
This high specificity is a major advantage over the traditional TB skin test (TST), which can produce false positives in people who received the BCG vaccine — common in many countries outside the United States. The QuantiFERON blood test is not affected by prior BCG vaccination, making it the preferred choice for immigrants, international travelers, and foreign-born individuals.
Can You Get a False Positive or False Negative?
False positives are uncommon but can occur in patients with prior exposure to Mycobacterium marinum, M. szulgai, or M. kansasii (non-tuberculosis mycobacteria). Borderline results in the 0.20–0.99 IU/mL range may require repeat testing.
False negatives can happen in immunocompromised patients, including those on immunosuppressive medications, people with HIV, or those with very recent TB exposure (the immune response needs 2–8 weeks to develop). If you have risk factors and receive a negative result but symptoms persist, your provider may recommend additional testing.
QuantiFERON TB Gold for Employment, Immigration, and School Requirements
Many employers, schools, and immigration agencies require TB clearance documentation. The QuantiFERON TB Gold test is accepted by:
- USCIS (Immigration) — accepted for immigration medical exams and green card applications
- Healthcare employers — required for annual TB screening of hospital and clinic staff
- Schools and universities — many California colleges require TB clearance for enrollment
- Food service employers — required for food handlers in many jurisdictions
- Childcare workers — California requires TB clearance for daycare and preschool staff
At CityHealth San Leandro, we provide same-day QuantiFERON testing with results in 1–3 business days and official documentation for your employer or school. No appointment needed — walk in or book online.
QuantiFERON vs. T-SPOT TB Test
Both the QuantiFERON and T-SPOT are interferon-gamma release assays (IGRAs), but they differ in methodology:
| Feature | QuantiFERON TB Gold Plus | T-SPOT.TB |
|---|---|---|
| Method | ELISA (measures IFN-γ concentration) | ELISPOT (counts IFN-γ producing cells) |
| Blood draw | 3–4 special tubes | 1 standard tube |
| Processing window | Must incubate within 16 hours | Must process within 8 hours |
| BCG interference | None | None |
| Indeterminate rate | Low (1–5%) | Low (1–5%) |
| FDA approved | Yes | Yes |
Both tests are equally acceptable for employment and immigration purposes. CityHealth offers QuantiFERON testing because it has more flexible processing requirements, making same-day walk-in testing easier for patients.
Frequently Asked Questions
Can I get the QuantiFERON test without a referral?
Yes. CityHealth offers the QuantiFERON TB Gold test without a referral. Just walk in or book online.
How long does it take to get results?
Most results are back within 2–5 business days after the blood draw.
Will I need to come back a second time?
No. That’s one of the main advantages of QuantiFERON over the skin test — one visit, one blood draw, done.
Does my employer have to accept QuantiFERON instead of a skin test?
In most cases, yes. QuantiFERON and the skin test are both CDC-approved and widely accepted. Confirm with your employer or institution before your visit to make sure either test is acceptable.
Is a positive QuantiFERON result the same as having TB?
No. A positive result indicates latent TB infection — meaning you’ve been exposed to the bacteria, but you don’t have active TB disease. Most people with LTBI never become sick. Treatment can reduce the risk of LTBI progressing to active disease.
CityHealth San Leandro — QuantiFERON TB Gold Testing
1401 Estudillo Ave, San Leandro, CA 94577
Mon–Fri: 8 AM – 8 PM | Sat–Sun: 9 AM – 5 PM
Single visit. No referral needed. Results in 2–5 business days.
Book Your TB Test Today
Need care today?
CityHealth urgent care in San Leandro offers same-day walk-in care — no appointment required. Book online or walk in.
