Tuberculosis QuantiFERON®-TB Gold Plus
The QuantiFERON®-TB Gold Plus test measures immune response to proteins associated with Mycobacterium tuberculosis in a blood sample. It is used as an aid in evaluating TB infection, read alongside risk assessment, radiography and other clinical evaluations rather than on its own.
About this test
This test is a blood-based interferon-gamma release assay, often called an IGRA. It measures the interferon-gamma that white blood cells release after exposure to a peptide cocktail that simulates TB-specific proteins, including ESAT-6, CFP-10 and TB7.
A whole blood sample is collected in a heparin tube. In the laboratory, the blood cells are stimulated with the TB-specific peptides, and the resulting interferon-gamma is measured by immunoassay.
Who might consider this test?
- A positive result is not read on its own; it calls for additional evaluation to distinguish latent infection from active disease.
Test details
| Quest code | 36970 |
|---|---|
| Methodology | Immunoassay |
| Sample type | 6 mL whole blood |
| Collection | Quest patient service center |
Reference range
Negative
Reference ranges are general guidance. The range printed on your own laboratory report is the one that applies to your result.
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Quest resources
Additional details
What this test looks at
The test reports interferon-gamma release measured against several controls, listed among the analytes as mitogen-nil, nil, TB1-nil and TB2-nil alongside the overall QuantiFERON result. It is listed under several names, including IGRA, QFT Plus, TB Gold and QFT TB, which all refer to this same assay.
How it's often used alongside other tests
This test is described as an aid in diagnosing M. tuberculosis infection, used in conjunction with risk assessment, radiography, and other clinical evaluations rather than by itself. A positive result is followed by additional testing to help distinguish latent TB infection from active TB disease, a step the clinician who ordered the test guides.
Order online and a physician order is included — no doctor's visit and no insurance needed. Your sample is collected at a Quest Diagnostics patient service center.
Laboratory results should always be interpreted by a licensed clinician who knows your health history. This page is information about a test, not medical advice.
Frequently asked questions
What does the QuantiFERON-TB Gold Plus test measure?
It measures interferon-gamma released by white blood cells after they are exposed to a peptide cocktail simulating TB-specific proteins. That release reflects an immune response associated with Mycobacterium tuberculosis exposure.
How is the sample collected?
The test uses a 6 mL whole blood sample collected in a heparin tube at a routine blood draw.
Do I need to prepare for this test?
No preparation instructions are listed for this test, though people follow any instructions their ordering clinician provides.
Is this the same as a TB skin test?
No. This is a blood-based interferon-gamma release assay, not a skin test. Guidelines describe it as preferred over a skin test for people vaccinated with BCG or unlikely to return for a follow-up reading.
What does a positive result mean?
A positive result is an aid in evaluating TB infection, not a diagnosis on its own. It calls for additional testing, alongside risk assessment and radiography, to distinguish latent infection from active disease.
Can I get the Tuberculosis QuantiFERON®-TB Gold Plus test without a doctor's visit or insurance?
Yes. The $215 cash price includes an independent physician's order, so no referral is needed, and insurance is never involved.