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PPD vs QuantiFERON TB blood test

QuantiFERON-TB Gold Plus is an interferon-gamma release assay, or IGRA, that checks an immune response to tuberculosis antigens in a blood sample. It is a different test from PPD.

A PPD test is also called a TB skin test, TST, or Mantoux test. Placement is the first visit; the test is not complete until trained staff read the reaction 48 to 72 hours later. TB blood testing, including QuantiFERON, uses a blood draw. CDC guidance prefers a TB blood test for people who received the BCG vaccine because BCG can affect a skin-test result.

A healthcare visit
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Nao Medical patient care
Match the test to the requirement PPD, two-step PPD, and TB blood testing are different workflows. Bring the exact form so the clinic can help you avoid the wrong visit path.

Choose the appropriate pathway

An IGRA is not affected by BCG vaccination in the way a skin test can be. The result can be positive, negative or indeterminate. An indeterminate result does not provide a useful answer and may require another test. Recent exposure or immune suppression can produce a negative result despite infection. An IGRA may be useful for people with BCG vaccination or those unlikely to return for a skin-test reading. Age and the requesting program's rules matter. CDC generally recommends a skin test for children younger than five while noting that some experts use blood tests. A clinician should choose the method for the child. Ask which option answers your clinical or documentation question and what would change after the result. Different tests and care settings are not interchangeable.

QuantiFERON and IGRA TB testing

QuantiFERON-TB Gold Plus is an interferon-gamma release assay, or IGRA, that checks an immune response to tuberculosis antigens in a blood sample. It is a different test from PPD. One collection visit can provide the sample, while interpretation and follow-up may need another contact.

Eligibility: QuantiFERON and IGRA TB testing

An IGRA may be useful for people with BCG vaccination or those unlikely to return for a skin-test reading. Age and the requesting program's rules matter. CDC generally recommends a skin test for children younger than five while noting that some experts use blood tests. A clinician should choose the method for the child.

What to expect: QuantiFERON and IGRA TB testing

Review prior results, treatment, exposure and symptoms before testing. The specimen has time-sensitive processing requirements. A positive result leads to an evaluation for TB disease. The blood test alone cannot distinguish latent infection from active TB or determine contagiousness.

Preparing for your appointment

Bring the school or employer requirement and previous TB records. Fasting is generally not the main preparation, but follow the collection team's instructions. Mention recent live-virus vaccination and a new exposure. Do not order repeat testing solely to replace a documented prior positive.

Risks and when to seek help

Do not assume a positive result is caused by BCG. Do not assume a negative test rules out TB in a symptomatic person. Contact the clinician about persistent cough, fever, night sweats or weight loss and disclose the concern before arrival.

Follow-up and treatment review

If recent exposure is suspected, the clinician may plan repeat testing after the immune response has had time to develop. Positive and indeterminate results need different next steps. Confirm who will complete the evaluation and return the report to the requesting program.

Appointments, costs and coverage

Confirm the current IGRA assay, collection schedule, laboratory network and expected reporting interval. Same-day collection does not promise same-day results or immediate school or employment clearance.

Questions about your care

Is QuantiFERON the same as PPD? Which TB test is better? Can I switch from PPD to QuantiFERON? Where can I book a QuantiFERON test?

Ask a nearby Nao Medical clinic for a TB-testing appointment and specify whether you need an IGRA blood test or a skin test. Confirm collection, the required form and any return visit before traveling. PPD is a tuberculin skin test with a return reading 48–72 hours later. QuantiFERON is an IGRA blood test with laboratory processing and no skin-test reading visit. The choice depends on age, BCG history, prior results and the requesting program; neither test alone distinguishes latent infection from active disease. Bring the exact requirement and prior records before switching tests.

What does a positive result mean?

A positive skin test or IGRA suggests TB infection; it does not by itself show active TB disease. The clinician reviews symptoms and history and may arrange chest imaging and other testing. An indeterminate IGRA is not a negative result and may need repeat or different testing. BCG vaccination does not cause a positive IGRA. Symptoms or a known exposure need prompt review.

Medical sources

Local PPD and TB testing locations

Related services and forms

QuantiFERON TB blood test

Use the TB blood-test guidance when your form asks for an IGRA, QuantiFERON, or TB blood draw instead of a skin test.

Occupational medicine

Work, healthcare, caregiver, and employer packets often combine TB testing with physicals, titers, vaccines, or other forms.

Vaccines and titers

School, healthcare, and immigration packets may ask for vaccine records or titers in addition to TB screening.

Lab tests and blood work

Use the lab-testing guidance when a broader blood-work panel, titer, or follow-up test is part of the requirement.

Immigration medical exams

USCIS medical exams have a separate process and pricing from routine PPD or employment TB testing.

DOT physicals

Drivers who need CDL or DOT documentation can review the DOT physical details for exam-specific requirements.

TB testing information by location