QuantiFERON-TB Gold Plus

QuantiFERON-TB Gold Plus

Alternate Test Name

Blood Assay for M. tuberculosis (BAMT); Interferon-gamma Release Assay (IGRA); Latent Tuberculosis Infection (LTBI); M. tuberculosis; Mycobacterium tuberculosis (MTB); QuantiFERON®-TB Gold In-Tube test; QFT; QFT-G; QFT-GIT; QFT-Plus; TB Infection Detection; Tuberculosis Screening Test

Epic Mnemonic
Sunquest Mnemonic

LAB2168
TBSCRN

Category

Sendouts

Methodology

Interferon-gamma release assay

Test Performance Schedule

Monday, Wednesday, Friday

Result Availability

2 – 4 days

Container

6.0 mL Green top (lithium heparin) tube

Volume

Pref. Vol.: 6.0 mL
Min. Vol.: 5.0 mL

Collection Instructions

• Routine venipuncture
• Mix by inverting tube 8 times
• Hold at room temperature for at least 15 minutes.
• Refrigerate within 3 hours

Transportation Instructions

Refrigerated

Stability

• Room Temperature: Unacceptable
• Refrigerated: 48 hours
• Frozen: Unacceptable

Causes for Rejection

Room temperature or frozen specimens

Remarks

Specimens must be received at Lakeland Laboratory within 24 hours of collection (contact Client Services if timing is questionable)

CPT Codes

86480

Effective/Revised

6/1/2020

The QuantiFERON-TB Gold Plus (QFT-Plus) assay is an Interferon Gamma Release Assay (IGRA) that antagonizes T-cells in heparinized whole blood and measures the release of interferon-gamma from these cells through an immune antigen response reaction. QFT-Plus additionally quantifies reacting CD4 and CD8 T-cells, with the latter more likely to be triggered during an active TB infection, and incorporates all measurements into an overarching, proprietary algorithm that provides a composite result of either positive, negative or indeterminate for active TB infection. The test utilizes two distinct TB antigen tubes: TB Antigen Tube 1 (TB1) and TB Antigen Tube 2 (TB2). TB1 contains peptides that stimulate CD4 T-cells and TB2 includes peptides that stimulate both CD4 and CD8 T-cells. This allows for the distinct enumeration of the proportion of interferon gamma that can be attributed to either the CD4 or the CD8 T-cells by subtraction or as a ratio. Moreover, the robustness of the CD4 response can also be enumerated by assessing the reproducibility of the response between the two tubes which is useful for identification of false positive results.