QuantiFERON-TB Gold Plus: How the TB Blood Test Works and What Your Results Mean

Who may need a TB blood test?

You may need a TB test for a healthcare job, school, college, or a clinical training program. Your provider may also recommend testing if you’ve had close contact with someone who has active TB or if you’ve lived in a country where TB is common.

SimrikMed offers TB blood testing for work, school, and exposure concerns. Call our office at (727) 606-3350 to confirm QuantiFERON-TB Gold Plus availability and arrange your visit.

What is the difference between inactive and active TB?

Inactive TB, also called latent TB infection, means TB bacteria are in your body, but you feel well and cannot spread TB to others. Treatment can help prevent the infection from becoming active later.

Active TB develops when the bacteria multiply and cause disease. When TB affects the lungs or throat, it can spread to others. A positive QuantiFERON result alone cannot tell whether TB is inactive or active.

How does QuantiFERON-TB Gold Plus work?

QuantiFERON-TB Gold Plus is a type of test called an interferon-gamma release assay (IGRA). After your blood is drawn, the lab measures how your immune cells respond to proteins from TB bacteria. The sample must be processed within a specific time, so call ahead to confirm when blood draws are available.

What do the results mean?

QuantiFERON result	What it means
Negative	TB infection is unlikely. If you have symptoms, a weakened immune system, or a recent exposure, your provider may recommend further evaluation.
Positive	TB infection is likely. Your provider will evaluate you for active TB, usually with a symptom review and a chest X-ray. A positive result by itself does not mean you are contagious.
Indeterminate	The test did not give a clear answer. Your provider may recommend repeating the blood test or getting a TB skin test.

If you were recently exposed, tell your provider when you last had contact with the person who had infectious TB. An early test can be negative even if you were infected. If your first test was negative, the CDC recommends repeating it 8 to 10 weeks after your last exposure.

What happens after a positive result?

Schedule a follow-up visit even if you feel well. Depending on your symptoms and chest X-ray, your provider may also order a sputum test, which checks mucus coughed up from your lungs. If the evaluation shows inactive TB, your provider will discuss treatment to reduce your risk of developing active disease.

Keep a written copy of your result and any treatment records. TB blood tests often remain positive after treatment, and these records may be helpful for future work or school screenings.

When should you call a provider?

Call your healthcare provider or local health department promptly if you have a cough lasting three weeks or longer, cough up blood, or have symptoms such as chest pain, fever, night sweats, or unexplained weight loss. Tell them about your symptoms before you arrive, even if a previous TB blood test was negative.

What should you bring to your visit?

• Your employer’s or school’s TB screening form and the date it is due.
• Any previous TB test results, especially a written record of a positive result.
• Records of previous TB treatment or BCG vaccination, if available.
• The date of your last known exposure, if you’re being tested after close contact with someone who had active TB.