Quantiferon Plus

TEST DESCRIPTION

Whole blood assay for the detection of latent and active tuberculosis by interferon-gamma release. A positive finding on Quantiferon Plus is strongly predictive of infection with Mycobacterium tuberculosis (MTB) complex. Blood samples are mixed with two MTB proteins and incubated for 16-24 hours; afterward the amount of interferon-gamma is measured as a signal of immune response. If the patient is infected with MTB, their white blood cells will release interferon-gamma in response to contact with the MTB proteins.

Methodology

Interferon-gamma release assay

Reference range

Negative

TEST FREQUENCY & RESULT AVAILABILITY

Performed weekly. Results are typically available on the Wednesday following specimen receipt.

ACCEPTABLE SPECIMEN TYPES AND COLLECTION

Whole blood collected into Quantiferon Plus collection tubes (4-tubes): 1 mL of whole blood per tube
Detailed collection instructions appear below

SPECIMEN STORAGE

Store at room temperature (17–25 °C/63 °F–77 °F) for up to 16 hours.

SPECIMEN TRANSPORT

Shipping conditions should follow the temperature and time requirements outlined above.

REJECTION CRITERIA

Tube volume and handling conditions outside acceptable range
Tubes not stored at room temperature
Level of blood outside black indicator line
Specimen tubes not labeled

CODES

CPT: 86480
LOINC: 71775-1
Test code: 8800

TEST FEE

Refer to the current fee schedule.

DETAILED SPECIMEN COLLECTION INSTRUCTIONS

QFT® Plus Blood Collection Tubes

Fill blood tubes to correct volume: The black mark on the side of the tubes indicates the 1 mL volume line. The Quantiferon Plus test has been validated for accuracy for tube volumes ranging from 0.8 to 1.2 mL. The 1 mL tubes fill slowly, so keep the tube on the needle for 2 - 3 seconds after the tube appears to have completed filling to ensure that the correct volume is drawn. If a “butterfly needle” is used, prime tubing with a “purge” tube before filling the QFT tubes to ensure proper fill volume.
Invert tubes 10 times: Immediately after filling the tubes, invert them 10 times just firmly enough to ensure that the entire inner surface of the tube is coated with blood. Overly vigorous shaking may cause gel disruption and could lead to aberrant results. It is essential that the blood mixes thoroughly with the antigens that have been dried onto the inner wall of the tubes.
Label tubes: Label each of the four tubes with the patient’s name & date of birth, as well as the collection date and time. Place the labeled collection tubes inside the zippered portion of the biohazard specimen bag and seal tightly.
Do not centrifuge, refrigerate, or freeze the blood tubes.
Complete Requisition Form: Fold it in half once and place in the outer pocket of the biohazard specimen bag (not with the tubes).
Transport at room temperature to the laboratory ASAP, but within 16 hours of collection.