Test Directory

QuantiFERON-TB Gold Plus, Blood

Print this page

Updated Test Information:

Test Description
QuantiFERON-TB Gold Plus, Blood
Synonym(s)

Latent TB, Latent Tuberculosis, LTBI, M. tuberculosis, Mycobacteria, Mycobacterium tuberculosis, PPD, QuantiFERON, QFT, Tb, MTb, Interferon-gamma, IFN-gamma, IGRA, Interferon-gamma release assay

Test ID
QFT4
General Information

Useful for:



  • Indirect test for Mycobacterium tuberculosis infection, to be used in conjunction with risk assessment, radiography, and other medical and diagnostic evaluations

  • This test is not recommended for use for diagnosis of active tuberculosis (TB) infection

Specimen Type

Whole Blood

Specimen Requirements

-Standard Altitude: QuantiFERON-TB Gold Plus Collection Kit (T794)
-High Altitude: QuantiFERON-TB Gold Plus High Altitude Collection Kit (T795)

Specimen Collection / Processing Instructions

Maintain tubes at room temperature (17°C 27°C) until incubation. Do not refrigerate or freeze. See special collections constructions on Mayo website: Collection & Processing Instructions

Additional Processing Details

4 mL: 1 mL per tube (4 tubes)

Stability

Before incubation:
Room Temperature (17°C–27°C): 16 hours


After incubation:
Refrigerated: 28 days

Unacceptable Specimen Conditions

Specimen submitted not following kit guidelines

Limitations

  • A negative QuantiFERON-TB Gold Plus (QFT-Plus) result does not preclude the possibility of Mycobacterium tuberculosis infection or tuberculosis disease. False-negative results can be due to the stage of infection (eg, specimen obtained prior to the development of cellular immune response), comorbid conditions that affect immune functions, incorrect handling of the blood collection tubes following venipuncture, or other individual immunological factors. Additionally, heterophile antibodies or nonspecific interferon-gamma (IFN-gamma) production from other inflammatory conditions may mask specific responses to ESAT-6 or CFP-10 peptides

  • A delay in incubation may cause false-negative or indeterminate results, and other technical parameters may affect the ability to detect a significant IFN-gamma response

  • A positive QFT-Plus result should not be the sole or definitive basis for determining infection with M tuberculosis. Positive results should be followed by further medical evaluation for active tuberculosis disease (eg, acid-fast bacilli smear and culture, chest X-ray)

  • While ESAT-6 and CFP-10 are absent from all bacille Calmett-Guerin (BCG) strains and from most known nontuberculous mycobacteria, it is possible that a positive QFT-Plus result may be due to infection with Mycobacterium kansasii, Mycobacterium szulgai, or Mycobacterium marinum. If such infections are suspected, alternative tests should be performed

  • The effect of lymphocyte count on reliability is unknown. Lymphocyte counts may vary over time for any individual person and from person to person. The minimum number required for a reliable result has not been established and may also be variable

  • The predictive value of a negative QFT-Plus result in immunosuppressed patients has not been determined

  • For healthcare personnel or patients who require baseline tuberculosis (TB) testing (at onboarding or entry into facilities) at the same time they are set to receive a coronavirus disease 2019 (COVID-19) mRNA vaccine,the Centers for Disease Control and Prevention (CDC) recommends the following:

    • PerformTB symptom screening on all healthcare personnel or patients

    • If using interferon-gamma release assays (IGRA), collect blood prior to COVID-19 mRNA vaccination

    • If using tuberculin skin test (TST), place prior to COVID-19 mRNA vaccination

    • If COVID-19 mRNA vaccination has already occurred, defer TST or IGRA until 4 weeks after completion of 2-dose COVID-19 mRNA vaccination



Methodology

Enzyme-Linked Immunosorbent Assay (ELISA)

Estimated TAT

2-4 days

Testing Schedule

Monday-Friday

Test Includes

  • QFTQ2: QuantiFERON-Tb Gold Plus Result

  • DEXQE: TB1 Ag minus Nil Result

  • DEXQF: TB2 Ag minus Nil Result

  • DEXQG: Mitogen minus Nil Result

  • DEXQH: Nil Result

CPT Code(s)

86481

Additional Information
Reference Range

Negative

Performing Lab

Mayo

LOINC Code(s)

71773-6, 64084-7, 88517-8, 71774-4, 71776-9