Quantiferon-TB Gold Blood Test

CERNER / EPIC MNEMONIC:

QNTFERTB

POE DESCRIPTION:

QNTFERTB

CPT CODE:

86480

CDM NUMBER:

3481116

TEST INFORMATION:

The Quantiferon-TB Gold (QFTB-G) is a test recommended for detection of the cellular immune response to infection with Mycobacterium tuberculosis, the agent that causes tuberculosis (TB).  This test performed on whole blood, detects active/latent tuberculosis and is more sensitive and specific than the tuberculin (PPD) skin test.  QFTB-G ordinarily provides a positive or negative result.
QFTB-G detects the release of interferon from memory lymphocytes in response to incubation with two mycobacterial proteins, ESAT-6 and CFP-10.  These antigens are not found in BCG vaccine or in most species of non-tuberculous and environmental mycobacteria.  Positive QFTB-G results may be observed in patients infected with Mycobacterium kansasii, Mycobacterium szulgai, and Mycobacterium marinum.  However, infections with these agents is uncommon.

DAYS PERFORMED:

Seven days a  week

TURNAROUND TIME:

72 HOURS

SPECIAL INSTRUCTIONS:

Please call laboratory (ext. 25452) on Saturday or Sunday before drawing patient.

CONTAINER TYPE:

Obtain a set of 3 QuantiFERON In-Tubes from the laboratory.  Please note all three tubes are REQUIRED for EACH QuantiFERON blood draw.  Tubes may be obtained from the Microbiology Laboratory (ext. 25452) or the Professional Building Laboratory  (ext. 25841) .  Do NOT use BD Heparin tubes

COLLECTION:

Each tube flll is 1 ml and the tubes MUST be drawn in the following order.  GRAY top tube first, RED top tube second, PURPLE top tube third.  If other blood work is also requested, collect the Quanti-Feron In-Tubes LAST.  If a butterfly is used, use a purge (throw away) tube so the tubing does not take up any of the required 1 ml volume in the first tube.  After collecting, shake all three tubes vigorously for 5 seconds until bubbles are seen in each tube.  Label each of the three tubes and include the time of collection.  Place all three tubes in one biohazard bag.

REJECTION CRITERIA:

Specimens collected in an inappropriate vacutainer tube.  Tubes must contain 1.0 ml of blood.  Specimens not received by the reference laboratory within 13 hours of collection.

MINIMUM VOLUME:

The tube must be as full as possible.  Specimens that are less than 1.0 ml will be rejected.

HANDLING INSTRUCTIONS:

Transport the specimen at room temperature to the Microbiology laboratory (ext. 25452, tube station 309) immediately after collection.  Specimens MUST be received by the referral laboratory within 13 hours of collection.

REFERENCE RANGE:

Not Detected

REFERENCE CHART:

DETECTED:  Infection with Mycobacterium tuberculosis likely

NOT DETECTED: Infection with Mycobacterium tuberculosis is unlikely but cannot be excluded, especially when illness is consistent with TB and the likelihood of progression to TB disease is increased.

INDETERMINATE: QFTB-G results cannot be interpreted as a result of low mitogen response or high background response.

LIMITATIONS OF TEST:

A negative result indicates that infection  with Mycobacterium tuberculosis is unlikely but cannot be excluded, especially when illness is consistent with TB and the likelihood of progression to TB disease is increased.  A disclaimer will be attached for patients less than 17 years of age.  The test has not been validated  for patients less than 17 years of age.

METHODOLOGY:

QFTB-G is a biologic assay that depends on the generation of interferon by memory lymphocytes that are exposed to Mycobacterium tuberculosis antigens.  Test results are determined by a mathematical algorithm and are reported as DETECTED, NOT DETECTED, OR INDETERMINATE

REFERRAL LABORATORY:

Quest Diagnostics Incorporated, Wood Dale 60191

TEST SYNONYM(S):TB blood test; Mycobacterium tuberculosis blood test