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Test Code LAB1232580 Quantiferon Gold Plus

Performing Laboratory

Asante Rogue Regional Medical Center (ARRMC)

 

Performing Department

Special Chemistry

Specimen Required

QuantiFERON Gold - Plus Blood Collection Tubes – Obtain collection tubes from RRMC central processing.

 

Order of draw: grey, green, yellow, purple. 

 

Quantiferon Gold Plus Collection Tubes

Specimen Minimum Volume

1 mL of blood into each of 4 Quantiferon tubes.

Specimen Stability Information

Collection

1. Using standard Venipuncture technique, collect 1 mL blood (0.8-1.2 mL) into each of the 4 tubes provided

    Kit (note the black fill line near bottom of tube).

  • Order of draw: grey, green, yellow, purple. 

  • Tubes fill slowly, keep the tube on the needle for 2-3 seconds once the tube appears to have completed filling. This will ensure that the correct column is drawn.
  • When the tube is upright, blood must meet the small black mark on the label. If the level of blood is outside the indicator mark, a new blood sample should be obtained.
  • Use of butterfly needle is NOT recommended. If a butterfly is required, first collect other required tubes or use a “purge” tube to remove the air. Then proceed with collecting the QTF-Plus tubes.
  • Under or overfilling of the tubes outside of the 0.8 to 1.2 mL range may lead to erroneous results. Blood should meet the small black mark on the label.

  • Quantiferon Gold Plus Collection Tubes

 

2. Immediately after filling the tubes, SHAKE the tubes firmly 10 times.

  • Entire inner surface of tube must be coated with blood. This will dissolve antigens on the tube walls.
  • Over-energetic shaking may cause gel disruption and could lead to aberrant results.

3. Label tubes appropriately—the label should be placed below the colored “QuantiFERON-TB” band  and so back window is visible on all 4 collection tubes.

4. MAINTAIN tubes at room temperature until incubation.

    It is recommended that INCUBATION start as soon as possible

    (and must be started within 16 hours of collection).

 

Phlebotomists can click the link to view the proper collection process for the 4 tube draw.

https://www.quantiferon.com/us/products/quantiferon-tb-gold-plus-us/training-videos/

 

Training video #1 explains the entire collection process. 

                          We will NOT be using the collection method used in training video #2.

 

Incubation & Centrifugation

1. INCUBATE all 4 tubes upright at 37ºC ±1 ºC for 16-24 hours.

  • Incubator is located in the Specimen Processing reference laboratory area.
  • If delayed from collection, re-mix tubes by again vigorously shaking 10 times immediately before incubation.
  • Improper incubation may cause erroneous results.
  • Do not use waterbath for incubation.
  • Humidity and CO2 are not required.
  • After Incubation tubes may be stored at 4-27ºC for up to 3 days prior to centrifugation, if necessary.

2. CENTRIFUGE tubes for 15 minutes 2000 or 3000 RCF (g) after incubation.

3. PLACE all 4 tubes together back in the QTB Biohazard Transport bag.

4. Store refrigerated 2-8ºC. Stable 28 days refrigerated.

 

Shipping

Ship QTB kit refrigerated 2-8ºC via courier to ARRMC Creekside Special Chemistry department

Reject Due To

  • Quantity not sufficient (QNS)
  • Lack of Two Patient Identifiers:
    • 1-Patient's First & Last name 
    • 2-Patient's Date of Birth
  • Not following collection guidelines
  • Overfilled

Day(s) Performed

Test Batched: Monday, Wednesday, and Fridays: AM shift

 

NOTE: Testing performed AFTER 16- 24 hour incubation period.

Method Name

Chemiluminescent Immunoassay technology (CLIA)

CPT Code Information

CPT Code: 86481

This test has been cleared or approved by the U.S. Food and Drug Administration and is used per manufacturer's instructions.

Billing Code

3020119

Clinical Information

Tuberculosis is a communicable disease caused by infection with M. tuberculosis complex organisms. A newly infected individual can become ill from tuberculosis within weeks to months, or can remain latently infected for years. Latent tuberculosis infection (LTBI) is a non-communicable asymptomatic condition, persisting in some who might develop tuberculosis disease months or years later. The main purpose of diagnosing LTBI is to consider medical treatment for preventing tuberculosis disease. The TST is a subjective test that can be falsely positive in individuals who are sensitive to tuberculin and have a positive TST result after being vaccinated with the bacilli Calmette-Guérin (BCG). In addition, some individuals may have weakened immune functions due to other conditions and do not respond to tuberculin.

The QuantiFERON®-TB Gold Plus (QFT Plus) test is a test for cell-mediated immune responses to peptide antigens that simulate mycobacterial proteins. These proteins, ESAT-6 and CFP-10 and are absent from all BCG strains and from most non-tuberculosis mycobacteria with the exception of M. kansasii, M. szulgai, and M. marinum. Individuals infected with M. tuberculosis complex organisms (M. tuberculosis, M. bovis, M. africanum, M. microti, M. canetti) usually have lymphocytes that recognize these mycobacterial antigens. This recognition process involves the secretion of cytokine, IFN- γ. The detection and quantification of IFN- γ forms the basis of the QFT Plus assay. The QFT Plus in-tube is an indirect in-vitro diagnostic test intended to aid in the diagnosis of latent tuberculosis caused by Mycobacterium tuberculosis. This is an FDA approved method using a cocktail simulating ESAT-6 and CFP-10 proteins to stimulate cells in heparinized whole blood. Detection of interferon-γ (IFN- γ) by ELISA is used to identify in-vitro responses to these peptide antigens that are associated with Mycobacterium tuberculosis infection.

 

 

Interpretation of Results:

This is a qualitative test. The TB1 and TB2 Antigen (Ag)-Nil IU/mL values should not be used to differentiate active from latent disease or to monitor disease progression or response to therapy.

Diagnosis or exclusion of tuberculosis (TB) and assessing the probability of latent tuberculosis infection (LTBI), require a combination of epidemiologic, historical, clinical, radiologic, and additional laboratory findings (eg, mycobacterial smear and/or culture) be taken into account when interpreting QuantiFERON-TB Gold Plus results.

The Nil value is used to determine the background, circulating interferon-gamma level in the patient. For the QuantiFERON-TB Gold Plus test to be valid, the nil value must be less than or equal to 8.0 IU/mL.

The mitogen minus nil value is used to assure that the patient is able to produce an interferon-gamma response to a universal stimulant (phytohemagglutinin). For the QuantiFERON-TB Gold Plus test to be valid, the mitogen value must be at least 0.5 IU/mL higher than the nil value.

The QuantiFERON-TB Gold Plus test is considered positive if the interferon-gamma response in the TB1 and TB2 antigen minus nil values are at least 0.35 IU/mL.

 

Limitations:

False-positive QuantiFERON-TB Gold Plus results may occur due to improper preanalytical processing of the QuantiFERON-TB Gold Plus tubes, prior infection with certain other mycobacteria (eg, Mycobacterium marinum, M kansasii, M szulgai) or biologic variability. Positive results should be confirmed with other clinical, exposure, and laboratory findings.

TB antigen minus nil values between 0.35 IU/mL and 1.1 IU/mL may represent false-positive results in individuals at low risk for latent tuberculosis infection (LTBI). Repeat testing on a new specimen or testing for LTBI by an alternative method is recommended.

A negative QuantiFERON-TB Gold Plus result does not preclude the possibility of Mycobacterium tuberculosis infection or tuberculosis disease. Falsely negative results can be due to the stage of infection, co-morbid conditions that affect immune functions, other individual immunological factors, improper blood sample collection or handling of the specimen affecting lymphocyte function. Blood must be incubated with stimulation antigens within 16 hours of collection. Delay in incubation may cause false-negative or indeterminate results.

The effect of lymphocyte count on reliability is unknown. Lymphocyte counts may vary from person to person. The minimum number required for a reliable result has not been established.

The performance of QuantiFERON-TB Gold Plus has not been evaluated in specimens from:

     - Individuals with impaired or altered immune functions (HIV infections, transplant patients, those receiving

       immunosuppressive drugs such as corticosteroids) and those with other clinical conditions (eg, diabetes,  

       hematological disorders)

     - Individuals younger than 17-years old

     - Pregnant women

The most recent Centers for Disease Control and Prevention recommendations for diagnosis of M tuberculosis infections (including disease) and selecting persons for testing can be found at www.cdc.gov/nchstp/tb

Additional Tests

QuantiFERON-TB Gold

Secondary ID

  • IGN-gamma
  • Latent Tuberculosis Infection (LTBI)
  • Mycobacterium tuberculosis (MTB)
  • Purified Protein Derivative (PPD)
  • QuantiFERON-TB Gold
  • Tubercle Bacilli: Mycobacterium tuberculosis
  • Tuberculosis (TB)
  • Interferon Gamma Release (IGRA)
  • QTB
  • QFT Plus
  • QTB Plus
  • QuantiFERON-TB Gold Plus