Quantiferon TB Gold, Blood

Diagnostic Use

QuantiFERON-TB Gold Plus (QFT) is a blood test assisting in the detection of Mycobacterium tuberculosis (MTB), the bacteria which causes tuberculosis (TB).
QFT is an interferon-gamma (IFN-γ) release assay (IGRA). QuantiFERON-TB Gold Plus (QFT) is an indirect test for M.tuberculosis infection (including disease) and is intended for use in conjunction with other diagnostic evaluations (radiography) and clinical evaluation and risk assessment.
QFT has a limited role in the diagnosis of TB. Positive Tuberculin skin tests and IGRA results do not distinquish between active TB disease and Latent TB infection (LTBI). A positive IGRA may help support a diagnosis of active TB in the appropriate clinical circumstance but is never conclusive.

Interferon Gamma Release Assay testing in patients aged five years and under require authorisation by a paediatric infectious diseases specialist or a microbiologist.
Specialist endorsement should be noted on the request form.Blood for IGRA testing can be taken on the paediatric day ward by paediatric registrars. For all other non-paediatric collections it is preferred to have the blood collected by phlebotomists.

The collection times for the test are strictly Monday-Thursday 0800-1600hrs.
No collection on Friday, Sat, Sun or Public Holidays.
It is important for test performance that the correct collection and initial processing procedures are strictly adhered to (please see the link to Test instructions below).
The QuantiFERON assay-specific collection tubes (4 set), as supplied by the laboratory, must be used. No other tubes are acceptable.
It is essential for the blood volume collected into each tube to be exactly 1ml.

Department

Microbiology - Serology

Delphic Registration Code

QTBN

Laboratory Handling

Phlebotomy

Monday-Thursday collects only. (No Friday, Sat, Sun or Public holiday collects) Bloods must be taken strictly no later than 16:00hrs. Specialised tubes with correct draws critical. *Do Not Refrigerate* Refer to "resources" below.

Registration

Immediate delivery to Lab at Room Temperature for correct incubation. *Do Not Refrigerate*

Separating

Requires incubation according to protocol before separating.

Laboratory

Samples to be inverted x 10 and incubated at 37C between 1100 - 1700.

Synonyms

IGRA
TB Gold

Turnaround Time

5 days

Specimen Type

• Whole Blood

Specimen Requirements

Tube/Container Type:

Preferred

• Quantiferon Kit

Preferred Sample Volume (ml)

1.0

Minimum Sample Volume (ml)

1.0

No of Samples Required

4

Pre-testing Requirements

Incubation must occur within 16hrs of collection. Samples that are not able to reach CHL within 16 hours require incubation according to protocol at referral laboratory.

Additional Specimen Information

Internal hospital clients - All samples are collected at BTC.
Local Christchurch clients. All samples need to be kept at room temperature and forwarded to CHL by 3.30pm Monday - Thursday
Out of Christchurch clients- Contact your local lab for tubes and instructions.

Samples must not be refrigerated
Collection tubes available from Serology CHL and BTC.

Special collection tubes and instructions attached - see link under Additional Information section below

Interferon Gamma Release Assay testing in patients aged five years and under require authorisation by a paediatric infectious diseases specialist or a microbiologist.
Specialist endorsement should be noted on the request form. Blood for IGRA testing can be taken on the paediatric day ward by paediatric registrars. For all other non-paediatric collections it is preferred to have the blood collected by phlebotomists.

The collection times for the test are strictly Monday-Thursday 0800-1600hrs.
No collection on Friday, Sat, Sun or Public Holidays

It is important for test performance that the correct collection and initial processing procedures are strictly adhered to (please see the link to Test instructions below).
The QuantiFERON assay-specific collection tubes (4 set), as supplied by the laboratory, must be used. No other tubes are acceptable.
It is essential for the blood volume collected into each tube to be exactly 1ml.

Aliquot Instructions

Additional Referral/Aliquot Information

The QuantiFERON assay-specific collection tubes (4 set), as supplied by the laboratory, must be used. No other tubes are acceptable.

Contact your local lab for specific tubes and instructions.

Interpretation

All interpretation inquiries to Microbiologist/Microbiology registrars. Collection enquiries to serology.

Tuberculosis is a Notifiable Disease

Reference Intervals

Reported as Negative or Indeterminate or Low Positive or Positive:

 

 

Test Method

Interferon Gamma Release Assay. Requires pre-incubation of blood samples before separating.

Non-Funded Test Cost

$77.21 (Exclusive of GST)

Billing Code

9425

The Guidelines for Tuberculosis Control in New Zealand 2019 contains information on the diagnosis, treatment and management of patients. Refer to resource link.

Resources

• Quantiferon TB GOLD Test instructions (148 KB)
• Guidelines for Tuberculosis Control in New Zealand 2019

Contact Information

Enquiry Form