Laboratory Test Reference Guide

Samples must be incubated within 16 hours of collection.

Prior to incubation store tubes at room temperature.

After incubation tubes may be held at 4-27°C for three days prior to centrifugation.

After centrifugation samples must be refrigerated.

Incubated and centrifuged tubes must be sent chilled.

Un-incubated tubes should be sent at ambient temperature.  They must reach the laboratory within 16 hours of collection.

Please indicate on specimen bag whether samples have been incubated or not.

QuantiFERON-TB Gold IT is an indirect test for M.tuberculosis infection (including disease) and is intended for use in conjunction with risk assessment, radiography and other medical and diagnostic evaluations.

The test has a very limited role in the diagnosis of TB. It should not be performed except in screening for latent TB infection in patients going on biologic therapy, or starting other immunosuppressants, or in the screening of TB contacts (see Guidelines for Tuberculosis Control in New Zealand 2019) in conjunction with Public Health)

The following approaches are recommended for different groups:

Contact screening for latent TB (LTBI):

• Contacts aged 5 years and under: use a Mantoux test, especially if under 2 years of age.
• Contacts > 5 years: use a Mantoux test or IGRA.
• People with a known previous positive IGRA or Mantoux should be tested with an IGRA.

Healthcare worker screening for LTBI:

• Use IGRA to screen health care workers for LTBI

Refugee screening for LTBI:

• Refugee children aged 5 years and under: use a Mantoux test
• Refugee children aged 6- 15 years and adults: Mantoux test or IGRA
• An IGRA is particularly recommended in: BCG Vaccinated children and immunocompromised children.

Screening for LTBI in immune-compromised people

• Use IGRA or Mantoux test to screen immunocompromised people where indicated.
• In some situations a clinician may elect to use both a Mantoux test and IGRA

An IGRA is particularly recommended in the following:

• BCG vaccinated people
• When it is considered a high risk the person will not return for the reading of their Mantoux
• When it is impractical for the person to make repeat visits for sequential testing
• When the contact has had LTBI or TB decline previously and has been tested with a mantoux test.

Criteria for performing Quantiferon TB Gold testing