Confident tuberculosis screening with QFT-Plus
QFT-Plus is blood test that helps identify people infected with M. tuberculosis (MTB), the causative agent of TB (tuberculosis). QFT-Plus is a modern alternative to the 110-year-old tuberculin skin test (TST).
How is the QuantiFERON-TB Gold Plus (QFT-Plus) TB blood test performed?
QFT-Plus measures the cell-mediated immune response to TB antigens to determine the likelihood of TB infection. It uses just 4 mL of blood – 1 mL per QFT-Plus Blood Collection Tube.
Available single-tube blood collection
Blood can be drawn into a standard lithium- or sodium-heparin tube and transferred to QFT-Plus tubes later, simplifying collection, improving patient experience and increasing flexibility.
A streamlined lab workflow
A lab-based ELISA assay lets you deliver results in just 24-28 hours, eliminating extra steps and second visits.
The QFT-Plus assay
The QFT-Plus assay is an in vitro diagnostic laboratory test that aids in the indirect detection of infection with MTB. It uses whole blood, with patented assay technology based on the measurement of -gamma (IFN-γ) secreted from stimulated T-cells previously exposed to MTB. It is a straightforward laboratory test that involves the following steps:
- Blood collection or transfer to the QFT-Plus Blood Collection Tubes
- Mixing of the QFT-Plus tubes to dissolve the testing antigens
- Incubation of the tubes at 37°C for 16–24 hours to stimulate interferon-gamma production
- Quantification of interferon-gamma using an enzyme-linked immunoassay (ELISA)
- Calculation of test results using optional QFT-Plus Analysis Software
Automated QuantiFERON TB testing is also available using the LIAISON QuantiFERON-TB Gold Plus CLIA assay.
TB testing workflow with QFT-Plus
Accurate QFT-Plus test results start with proper blood collection and handling. After collection, blood is incubated in the QFT-Plus tubes at 37°C for 16 to 24 hours. Plasma is harvested after incubation and tested for the presence of IFN-γ produced in response to the peptide antigens.
The QFT-Plus test can be performed in each of the following ways, depending on the logistical requirements of the phlebotomy site and the testing laboratory:
Option 1: Direct blood draw into QFT-Plus blood collection tubes
Collect 1 ml of whole blood directly into each of four QFT-Plus blood collection tube and hold at room temperature (17–25°C) for up to 16 hours prior to incubation.
Direct draw into QFT-Plus Blood Collection Tubes
Step 1: Draw 1 ml of blood to each of the four QFT-Plus Blood Collection Tubes.
Step 2: Shake 10 times to dissolve the testing antigens.
Step 3: Hold or transport samples at room temperature for up to 16 hours prior to incubation.
Step 4: Incubate the samples at 37°C for 16–24 hours.
Option 2: Blood draw into a single lithium- or sodium-heparin tube
Draw at least 5 ml of blood into a single blood collection tube containing lithium or sodium heparin as the anticoagulant. Blood drawn into a lithium- or sodium- heparin tube and maintained at room temperature must be transferred to QFT-Plus Blood Collection tubes and incubated within 16 hours from the time of collection.
Option 1 – Lithium or sodium-heparin tube room temperature storage and handling
Step 1: Draw at least 5 ml of blood to single lithium- or sodium-heparin tube
Step 2: Transfer 1 ml of blood to each of the four QFT-Plus Blood Collection Tubes within 16 hours
Step 3: Shake 10 times to dissolve the testing antigens.
Step 4: Incubate the samples at 37°C for 16–24 hours.
Option 2 – Lithium or sodium-heparin tube refrigerated storage and handling
Step 1: Draw at least 5 ml of blood to a single lithium- or sodium-heparin tube.
Step 2: Refrigerate the blood at 2–8°C.
Step 3: Transfer 1 ml of blood to each QFT-Plus Blood Collection Tubes within 53 hours of collection.
Step 4: Shake 10 times to dissolve the testing antigens.
Step 6: Incubate the samples at 37°C for 16–24 hours.
For complete instructions for use, consult the QuantiFERON-TB Gold Plus (QFT-Plus) Package Insert.
Learn more about how to perform QFT-Plus blood collection
Choose the testing process that works for you and your partners
Flexible QFT-Plus blood collection options help you choose a workflow that fits your testing requirements. Some examples of possible blood collection workflows include:
Sample incubation at the blood draw site with room temperature handling:
- Draw blood into QFT-Plus tubes at room temperature (17–25°C) and place them in a 37°C incubator within 16 hours.
- Incubate QFT-Plus tubes in a 37°C incubator at the blood collection site for 16–24 hours.
- Ship incubated samples to the testing lab at between 4°C and 27°C within 3 days.
Sample incubation at the testing lab after shipping with room temperature handling:
- Draw blood into QFT-Plus tubes and ship samples to the testing lab at room temperature (17–25°C) so that they arrive within 16 hours.
- Incubate QFT-Plus tubes in a 37°C incubator at the testing lab for 16–24 hours.
Refrigerated shipping and handling:
- Draw blood into a lithium- or sodium-heparin tube and refrigerate within 3 hours.
- Hold, handle and ship samples to the testing lab at a temperature of 2–8°C within 48 hours
- Return samples to room temperature, transfer to QFT-Plus tubes and place in a 37°C incubator at the testing lab within 2 hours
- Incubate QFT-Plus tubes in a 37°C incubator at the testing lab for 16–24 hours.
Additional technical help for testing labs
QuantiFERON-TB Gold Plus Blood Collection Tubes by QIAGEN and LIAISON Analyzer by DiaSorin.