Mycobacterium tuberculosis Infection by QuantiFERON-TB Gold


Sunquest Code:QTB  
Epic Code:LAB5701Epic Name:M Tuberculosis by Quantiferon
Order Instructions:UMMC-East inpatient samples are sent to the Acute Care Laboratory for processing. NOTE: This testing is being phased out as of June 2018. Please refer to test QPLUS-Mycobacterium tuberculosis by Infection by QuantiFERON TB Gold Plus
Synonyms:Latent TB; Latent tuberculosis; LTBI; M. tuberculosis; Mycobacteria; Mycobacterium tuberculosis PPD; QuantiFERON; QuantiFERON-TB; QuantiFERON-TB Gold; TB; Tuberculosis, QFT
Methodology:Interferon-y release assay (IGRA) by enzyme-linked immunosorbent assay (ELISA)
CPT Code:----------CPTCODES HERE----------
Turnaround Time:Performed Mon-Fri; results are reported within 2-4 days.


Collection Instructions

Specimen:Blood
Optimal Volume:1.0 mL in each of three tubes from QTB collection kit
Minimum\Peds Volume:0.8 mL in each of three tubes from QTB collection kit
Collection Instructions:
   
  1. QTB tubes should be the last tubes collected during a blood draw.
  2. Collect 1 mL of blood into each of the 3 QFT collection tubes. Tubes must be filled together as a group in the following order:
    a. Gray (NIL)
    b. Red (TB Antigen)
    c. Purple (Mitogen)
    Tubes should be at 17-25°C (63-77°F) at the time of collection. Note that tubes fill slowly.
  3. Tubes are manufactured to draw 1 mL of blood. Under or overfilling of the tubes outside of the 0.8-1.2 mL range may lead to erroneous results. If the level of blood is not close to the black indicator line, another specimen should be collected.
  4. Use of butterfly needle is NOT recommended. If butterfly is required; first collect other required tubes or use a "purge" tube to remove the air. Then proceed with collection of the QTB tubes.
  5. Immediately after filling tubes, shake them ten (10) times just firmly enough to ensure the entire inner surface of the tube is coated with blood, to solubilize antigens on tube walls. Over-energetic shaking may cause gel discuption and could lead to aberrant results.
  6. Label each tube using a long name label. Do not use small peon labels. Ensure that the fill line indicator and blood volume remains visible for assessment.
   
Causes for Rejection:Specimens other than those collected and processed according to instructions in the QuantiFERON-QTB Gold In-Tube Collection Kit.


Processing and Shipping

Specimen Processing:
Note: UMMC-East inpatient samples are sent to the East Core Lab for processing.
  1. Maintain tubes at room temperature until incubation. It is recommended that incubation start as soon as possible and must be started wtihin 16 hours of collection.
  2. INCUBATE all 3 tubes upright at 37°C for 16-24 hours. If delayed from collection, re-mix tubes by inverting 10 times before incubation. (Improper incubation may cause erroneous results. Humidity and CO2 are not required.)
  3. After incubation, centrifuge tubes for 15 minutes at 3000 RCF (g).
  4. Place all 3 tubes together back in the original QTB transport bag and label "incubated".
  5. Store and ship at refrigerated temperatures.
Shipping Instructions:Ship incubated samples at refrigerated temperatures in a labeled QTB transport bag. Ship non-incubated samples at room temperature within 12 hours.
Test Performed at or Referral Lab Endocrine  (UMMC-East Bank)


Interpretive

Reference Range:By report.
Use:

Aid in diagnosis of Mycobacterium tuberculosis infection, including latent tuberculosis infection (LTB1) and tuberculosis (TB) disease. QFT-G can be used in all circumstances in which the tuberculin skin test is currently used, including contact investigations, evaluation of recent immigrants who have had BCG vaccination and TB screening of health care workers and others undergoing serial evaluation for M. tuberculosis. However, caution should be used when testing certain populations because of limited data in the use of QFT-G.

 

New guidelines around TB testing were published on Dec 12, 2016 in Clinical Infectious Disease®2017;64(2):111-5. The new guidelines were the outcome of a task force made up of the American Thoracic Society (ATS), the US Centers for Disease Control and Prevention (CDC), and the Infectious Diseases Society of America (IDSA). These three organizations joined forces to broaden the preferential recommendation of modern blood-based TB tests over the 100 year old tuberculin skin test (TST). The task force recommends performing an interferon-g release assay (IGRA) rather than a tuberculin skin test (TST) in individuals >5 years old who meet the following criteria:

·          Those likely to be infected with Mycobacterium tuberculosis

·          Anyone with low or intermediate risk of disease progression.

·          Those who it has been decided that LTBI testing is warranted.

·          BCG-vaccinated individuals or those unlikely to return for their TST reading.

 

 



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