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Beaumont Laboratory

QuantiFERON-TB

QFT-TB, EPIC: LAB5784, SOFT: QFTTB

Instructions

  • Collection Days: MONDAY-THURSDAY ONLY.
  • SPECIMENS FOR OUTPATIENT QFT-TB ORDERS MUST BE COLLECTED AT ONE OF THE FOLLOWING OUTPATIENT LABORATORIES AT THE ROYAL OAK,Grosse Pointe, TROY or FARMINGTON HILLS CAMPUS:
    • Royal Oak Medical Office Building Outpatient Laboratory: Monday - Thursday, 7:00 a.m. - 6:00 p.m.
    • Royal Oak Imaging Center Outpatient Laboratory: Monday - Thursday, 7:00 a.m. - 5:00 p.m.
    • Royal Oak Cancer Center Outpatient Laboratory: Monday - Thursday, 8:00 a.m. - 4:30 p.m.
    • Sterling Heights Outpatient Service Center (across from Troy Beaumont Hospital): Monday - Thursday, 7:00 a.m. - 4:00 p.m.
    • Grosse Pointe Hospital Outpatient Laboratory: Monday - Thursday, 7:00 a.m. - 4:00 p.m.
    • Grosse Pointe Medical Office Building Outpatient Laboratory: Monday - Thursday, 7:00 a.m. - 4:00 p.m.
    • Troy Hospital Area B Laboratory: Monday - Thursday, 7:00 a.m. - 4:00 p.m.
    • Farmington Hills Main Laboratory: Monday - Thursday, 7:00 a.m. - 3:00 p.m.
    • Farmington Hills North Professional Satellite: Monday - Thursday, 7:00 a.m. - 3:00 p.m
  • For INPATIENTS, this test is only orderable Monday - Thursday, 7:00 a.m. - 6:00 p.m. at the Royal Oak Hospital and 7:00 a.m. - 4:00 p.m. at Grosse Pointe Hospital and 7:00 a.m. - 4:00 p.m. at the Troy Hospital and 7:00 a.m. - 3:00 p.m. at the Farmington Hills Hospital; Lab Collect only.

Specimen Collection Criteria

SPECIMEN COLLECTION INFORMATION

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

  1. Nil Tube (negative control): Gray.
  2. TB Antigen Tube: Red.
  3. Mitogen Tube (positive control): Purple.

SPECIMEN COLLECTION PROCEDURE

  1. Place a label on all three QFT-TB 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 3 QFT-TB collection tubes in the following order: Nil tube (Gray), TB antigen tube (Red), Mitogen tube (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 three 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 three 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.

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 Royal Oak, Troy or Farmington Hills will be rejected.

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
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, Wednesday, 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. In comparison to the Tuberculin Skin Test (TST), QFT-TB exhibits a similar specificity for excluding LTBI (99.8% QFT-TB vs. 99.8% TST) but an increased sensitivity for confirming LTBI (89% QFT-TB vs. 76% TST).

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 Code

86481.

Test Codes

EPIC: LAB5784, SOFT: QFTTB

Last Updated

08/11/2017

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This directory currently reflects information only for specimens collected and/or processed at the Farmington Hills, Grosse Pointe, Royal Oak, and Troy campuses.