Why You May Need a TB Test Before Biologics or Immunosuppressants
Learn why some immune-modifying medications require TB evaluation before treatment and what a positive, negative, or indeterminate result can mean for the next step.
Medically reviewed by Rhonda Collins, FNP-C | Mito Health on August 28, 2026.
Some biologics and other immune-modifying medications require a tuberculosis evaluation before treatment begins. The reason is not that the medication causes TB. Suppressing parts of the immune response can allow an inactive TB infection to progress or make a new infection more serious. The exact test, timing, and follow-up depend on the medication, your health history, and your prescriber’s protocol.
Do not start, stop, or delay a prescribed medication based only on this article or a self-ordered test. Follow the prescribing clinician’s instructions.
Why can immune-modifying treatment change TB risk?
After TB germs enter the body, the immune system can keep them controlled without symptoms. This is often called inactive or latent TB infection. Some medications reduce the immune activity that helps maintain that control, increasing the chance that infection progresses to active TB disease.
Tumor necrosis factor, or TNF, blockers are a representative example. Current FDA prescribing information for Humira warns about serious infections, including TB, and directs clinicians to evaluate and test for latent TB before treatment. It also calls for monitoring during treatment, including in people who tested negative before starting.
That example does not mean every biologic or immunosuppressant follows the same rule. Medication labels and specialty protocols differ. Your prescriber should identify the evaluation required for the specific treatment under consideration.
What does pre-treatment TB screening involve?
Screening may include a review of prior TB infection or treatment, exposure history, travel or residence history, symptoms, and a TB blood or skin test. People with symptoms or a positive test need medical evaluation for active TB disease. A prescriber may also need prior records or further testing before deciding whether treatment can begin.
QuantiFERON-TB Gold Plus is a TB blood test, also called an interferon-gamma release assay or IGRA. It can show whether the immune response supports TB infection. It cannot determine by itself whether an infection is inactive or has progressed to active TB disease.
The CDC’s clinical testing guidance states that people with a positive TB blood or skin test need further evaluation to rule out active TB disease. Testing should be paired with a plan for evaluation and treatment when indicated.
What happens after a positive result?
A positive result usually supports TB infection, but it does not diagnose active TB disease. Your prescriber must interpret it alongside your symptoms, medical history, medication plan, and any additional evaluation. The next step may include a physical examination, chest imaging, or other testing directed by your care team.
The result can affect when an immune-modifying medication starts, but that decision belongs to the prescribing clinician. Do not change your treatment schedule yourself.
What happens after a negative result?
A negative result makes TB infection less likely. It is not a permanent guarantee against future infection, and it does not override symptoms, recent exposure, or a weakened immune response.
If you were exposed recently, the test may have been performed before infection became detectable. Contact a clinician or health department promptly rather than waiting on your own. Depending on the exposure, repeat testing may be recommended 8 to 10 weeks after it ended. The timing is explained in when to test for TB after exposure.
FDA labeling for TNF blockers also makes clear that monitoring does not end with one negative pre-treatment test. Your prescriber may reassess risk or symptoms during treatment.
What does an indeterminate result mean?
An indeterminate QuantiFERON result does not establish whether TB infection is present. It means the test’s controls and responses did not support a positive or negative classification. Your prescriber may recommend repeating the blood test, using a skin test, or proceeding with other evaluation based on your risk and the urgency of the medication plan.
Do not assume that an indeterminate result is the same as a negative result. The clinician managing the medication needs to decide what evidence is sufficient before treatment starts.
Should you order a blood test or get a skin test?
Both TB blood tests and skin tests can test for TB infection. A blood test requires one collection visit and is preferred for many people who received the BCG vaccine. A skin test requires a return visit for reading and remains acceptable in some settings. Compare the TB blood test and PPD skin test workflows before choosing a route, but follow the test method specified by your prescriber.
If your prescriber confirms that QuantiFERON-TB Gold Plus fits the required evaluation, Mito offers the exact Tuberculosis Blood Test (QuantiFERON-TB Gold Plus). The laboratory result still needs to return to the prescribing clinician for interpretation before you act on the medication plan.
This article is for educational purposes and does not replace medical advice, diagnosis, or treatment.