QuantiFERON®-TB Gold Plus : 36970

This test can only be used for the one-tube collection method.

Test Code
TBPLUS or 36970

CPT Codes

Green top Lithium Heparin Blood collection tubes must be at room temperature (17-25°C) at the time of collection.

Caution:  Lithium Heparin is the only acceptable heparin tube.  Other anticoagulants will interfere with the assay.

Transport Container
Draw into Single 6 mL Lithium Heparin tube (5 mL minimum):
a) Collect whole blood into a 6mL Lithium Heparin collection tube and gently mix by inverting the tube several times to dissolve the heparin.
b) Blood drawn into lithium-heparin tube may be refrigerated (2-8°C) immediately after collection. Place tube in QuantiFERON®-TB Gold Plus transport bag for transport.
c) Blood drawn into lithium-heparin tube should not be held at room temperature (17-25°C) for longer than 3 hours after collection prior to refrigeration.

Transport Temperature

Specimen Stability
Ambient: 3 hours; Refrigerated: 48 hours; Frozen: Unacceptable

Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Anticoagulants other than Lithium Heparin; Lithium Heparin gel separator tube (PST).

Interferon Gamma Release Assay (IGRA) measured by ELISA

Setup Schedule
Monday & Wednesday & Friday

Report Available
2 to 5 days

Reference Range

Clinical Significance
QuantiFERON-TB Gold Plus (QFT-Plus) test is the fourth generation in QuantiFERON-TB testing technology assessing cell-mediated response through a quantitative measurement of IFN-γ in a whole blood sample. QFT-Plus is a test that measures the cell-mediated immune (CMI) responses to peptide antigens that simulate mycobacterial proteins. These proteins, ESAT-6 and CFP-10, are absent from all BCG strains and from most non-tuberculosis mycobacteria with the exception of M. kansasii, M. szulgai and M. marinum. Individuals infected with M. tuberculosis complex organisms usually have lymphocytes in their blood that recognize these and other mycobacterial antigens. This recognition process involves the generation and secretion of the cytokine, IFN-γ. The detection and subsequent quantification of IFN-γ forms the basis of this test.
In M. tuberculosis (MTB) infection, CD4+ T cells play a critical role in immunological control through their secretion of the cytokine IFN-γ. Evidence now supports a role for CD8+ T cells participating in the host defense to MTB by producing IFN-γ and other soluble factors, which activate macrophages to suppress growth of MTB, kill infected cells, or directly lyse intracellular MTB. IFN-γ producing MTB-specific CD8+ cells have been detected in subjects with LTBI and with active TB. Moreover, ESAT-6 and CFP-10 specific CD8+ T lymphocytes are described as being more frequently detected in subjects with active TB disease versus LTBI, and may be associated with a recent MTB exposure. In addition, MTB-specific CD8+ T cells producing IFN-γ have also been detected in active TB subjects with HIV co-infection and in young children with TB disease.
Unlike QFT, the QFT-Plus has two distinct TB antigen tubes: TB Antigen Tube 1 (TB1) and TB Antigen Tube 2 (TB2). Both tubes contain peptide antigens from the MTB-complex-associated antigens, ESAT-6 and CFP-10. Both the TB1 tube and TB2 tubes contain peptides from ESAT-6 and CFP-10 that are designed to elicit CMI responses from CD4+ T-helper lymphocytes; the TB2 tube contains an additional set of peptides targeted to the induction of CMI responses from CD8+ cytotoxic T lymphocytes.
Tuberculin skin test and IGRA tests are helpful but insufficient for diagnosing M. tuberculosis complex infection in sick patients – a positive result can support the diagnosis of tuberculosis disease (TB); however, infections by other mycobacteria (e.g., M. kansasii) could also cause positive results. Other medical and diagnostic evaluations are necessary to confirm or exclude tuberculosis disease.
Risk factors for M. tuberculosis infection include historical, medical, or epidemiological predictors for tuberculosis disease or exposure to tuberculosis. Refer to the most recent CDC guidance (https://www.cdc.gov/tb/publications/guidelines/default.htm) for detailed recommendations about diagnosing M. tuberculosis infection (including disease) and selecting persons for testing. QFT-Plus has been tested in some patient groups indicated for screening for TB infection according to current ATS/CDC guidance, including: persons who have tested positive for human immunodeficiency virus (HIV), contacts of recent TB patients and residents in high congregate settings who have been exposed to adults at high- risk of TB.

Performing Laboratory
med fusion

The CPT Codes provided in this document are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed. Any Profile/panel component may be ordered separately. Reflex tests are performed at an additional charge.