Lab Test

QuantiFERON-TB

QFT-TB, IGRA, Interferon Gamma Release Assay

Test Codes

EPIC: LAB5784, SOFT: QFTTB

Department

Special Chemistry

Instructions

INPATIENT COLLECTION
Collection Days: 24 HOURS PER DAY, 7 DAYS A WEEK. For additional information, please contact Client Services (1-800-551-0488, option 5).

OUTPATIENT COLLECTION
Due to the pre-analytical sensitivity of the QFTB Gold test specimen collection must occur at the following Patient Service Center locations during the listed days and times only.

Allen Park Beaumont Laboratory:   Monday – Friday, 7:30 am – 3:00 pm
Belleville Beaumont Healthcare Center (Currently Closed):  Monday – Friday, 8:00 am – 2:00 pm
Brownstown Beaumont Healthcare Center:   Monday – Friday, 8:00 am – 3:00 pm
Canton Beaumont Healthcare Center:   Monday – Friday, 6:30 am – 5:00 pm
Dearborn Hamlet Medical Building:  Monday – Friday, 6:30 am – 3:00 pm
Dearborn Beaumont Dearborn Medical Park:  Monday – Friday, 7:00 am – 5:30 pm
Dearborn Beaumont Hospital, Suite 107:  Monday – Friday, 7:00 am – 4:30 pm;  Saturday, 7:30 – 11:30 am
Dearborn (Formerly Oakdale):   Monday – Friday, 8:00 am – 1:30 pm
Farmington Hills Main Laboratory: 7:00 am – 3:00 pm
Farmington Hills North Professional Satellite: 7:00 am – 3:00 pm
Farmington Hills Hospital Inpatient collections: 7:00 am – 3:00 pm
Grosse Pointe Outpatient Laboratory: 7:00 am – 4:00 pm
Grosse Pointe Medical Office Building Outpatient Laboratory: 7:00 am – 4:00 pm
Grosse Pointe Hospital Inpatient collections: 7:00 am – 4:00 pm
 Royal Oak Medical Office Building Outpatient Laboratory: 7:00 am – 6:00 pm
Royal Oak Imaging Center Outpatient Laboratory:  7:00 am – 5:00 pm
Royal Oak Cancer Center Outpatient Laboratory:  8:00 am – 4:30 pm
Royal Oak Hospital Inpatient collections:  7:00 am – 6:00 pm
Southgate Beaumont Healthcare Center:  Monday – Friday, 7:00 am – 6:00 pm
Taylor Beaumont Hospital:  Monday – Friday, 8:00 am – 12:00 pm
Trenton Beaumont Hospital: Monday – Friday, 7:00 am – 5:30 pm,  Saturday 7:30 am – 11:30 pm
Sterling Heights Outpatient Service Center (across from Troy Beaumont Hospital): 7:00 am – 4:00 pm
Troy Hospital Inpatient collections: 7:00 am – 4:00 pm
Wayne Beaumont Hospital:  Monday – Friday, 8:00 am – 3:30 pm
Westland Beaumont Healthcare Center:  Monday – Friday, 8:00 am – 4:00 pm
Woodhaven Beaumont Internal Medicine:  Monday – Friday, 7:00 am – 2:00 pm

**All specimens that are routed to Dearborn must be shipped in a green specimen bag. 

**These collections cannot be placed in an outdoor specimen lock box due to specimen stability requirements.

Specimen Collection Criteria

SPECIMEN COLLECTION INFORMATION

Collection Tubes: The QFT-TB Gold Plus test uses four distinct tubes provided as a set that are labeled and color coded as follows:

  1. Nil Tube: Gray.
  2. TB1 Antigen: Green.
  3. TB2 Antigen: Yellow.
  4. Mitogen: Purple.

SPECIMEN COLLECTION PROCEDURE

  1. Place a label on all four QFT-TB Gold Plus collection tubes (all labels that print are identical). Affix a separate label to the special instructions card associated with each tube set.
  2. Collect specimen using the four QFT-TB Gold Plus collection tubes in the following order: Nil tube (Gray), TB1 Antigen tube (Green), TB2 Antigen (Yellow), Mitogen (Purple).
  3. The QFT-TB collection tubes are manufactured to draw approximately 1.0 mL. The black mark on the side of each tube indicates the 1.0 mL fill volume. For each patient, collect 1.0 mL of blood by venipuncture directly into each of the four tubes. To ensure that the correct volume is drawn, keep the tube on the needle for 2-3 seconds once the tube appears to have completed filling.
  4. Immediately after filling, shake tubes ten times using a hand shaking motion, in which one shake constitutes an up and down motion. Shake just firmly enough to ensure the entire inner surface of each tube is coated with blood. Frothing of the blood is commonly observed after shaking.
  5. Place tubes back in the biohazard bag and complete the special instructions card confirming step four was performed adequately.
    • DO NOT CENTRIFUGE TUBES.
    • DO NOT REFRIGERATE TUBES. 
  6. Send specimens at room temperature to the Core Laboratory via the Pneumatic Tube system (Royal Oak #266), Specimen Processing (Troy) or the Main Laboratory (Farmington Hills) for further processing. 
  7. Taylor, Trenton and Wayne incubate and spin the tubes before sending for testing to Royal Oak. These specimens must be transported as refrigerated specimens.

Rejection Criteria

  • Specimens must be collected using tubes manufactured specifically for QFT-TB testing described under Specimen Collection Criteria. Other tubes used for collection will be rejected.
  • Specimens for outpatient orders NOT collected at an Outpatient Laboratory at Beaumont Hospital in Farmington Hills, Grosse Pointe, Royal Oak, or Troy will be rejected.

In-Lab Processing

Do not centrifuge or refrigerate specimens.

Storage

Specimen Stability for Testing:

Room Temperature (20-26°C or 68-78.8°F): 16 hours
Refrigerated (2-8°C or 36-46°F): Unacceptable (Except Taylor, Trenton, Wayne specimens that are processed as indicated above.)
Frozen (-20°C/-4°F or below): Unacceptable

Specimen Storage in Department Prior to Disposal:

Refrigerated (2-8°C or 36-46°F): 7 days

Laboratory

Royal Oak Special Testing Laboratory

Performed

Monday – Friday.
Results available 2-6 days after collection.

Reference Range

Negative.

Test Methodology

ELISA (Assayed analyte – Interferon gamma).

Interpretation

  1. Negative – M. tuberculosis infection not likely: A negative result does not exclude M. tuberculosis infection particularly for individuals with impaired immune function. Epidemiological history and current medical status must be considered when assessing the probability of latent TB infection.
  2. Indeterminate for TB antigen responsiveness: An indeterminate result may be related to the immune status of the individual being tested. Consider repeat testing if clinically appropriate.
  3. Positive – M. tuberculosis infection likely: A false-positive result may occur in individuals infected with M. kansasii, M szulgai or M. marinum (non-tuberculous strains). Epidemiological history and current medical status must be considered when assessing the probability of latent TB infection.

Clinical Utility

QuantiFERON-TB testing provides an assessment of cell-mediated immunity to peptide antigens that simulate Mycobacterium tuberculosis proteins. T lymphocytes from individuals with active or latent tuberculosis infection (LTBI) will secrete interferon gamma (when stimulated in vitro by those antigenic components. The QFT-TB test system measures mycobacterium-specific interferon gamma release as an endpoint for determining exposure to M. tuberculosis. The overall sensitivity and specificity for QFT-TB Gold Plus is 94.81% and 98.09%, respectively (QuantiFERON-TB Gold Plus package insert, 08/2017).

RECOMMENDED INDICATIONS FOR QFT-TB TESTING:

In Health Care Workers (HCWs) for evaluation of:

  • Latent tuberculin infection (LTBI) in foreign born HCWs and individuals who have been vaccinated with BCG.
  • LTBI in new HCWs over 50 years of age.
  • LTBI in HCWs with chronic medical conditions.
  • HCWs that have converted their TST and do not have an identified exposure.

Patients – it may be appropriate to test the following individuals for LTBI:

  • Compromised by disease (e.g. malignancy, connective tissue disorders).
  • Compromised by medications (e.g. glucocorticoids, anti-TNF).
  • Dialysis patients and transplant population (donor/recipient).
  • When TB is suspected and the TST is negative.

Test Limitations:

  • QFT-TB has only limited advantages over TST in individuals who are not foreign born, have not been vaccinated with BCG, or in immunocompromised patients where the test is less sensitive.
  • QFT-TB does not distinguish between active and latent tuberculosis infection.

Disease Reporting

Mycobacterium tuberculosis.

Reference

  1. Andersen P et al. Specific immune-based diagnosis of tuberculosis. Lancet, 2000. 356; 1099-1104.
  2. Diel R et al. Interferon-gamma release assays for the diagnosis of latent Mycobacterium tuberculosis infection: A systematic review and meta-analysis. European Respiratory Journal, 2011. 27; 88-99.

CPT Codes

86480

Contacts

Last Updated

7/18/2022

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