Assay

Quantiferon-TB (Interferon Gamma releasing Assay)

Key Words

Quantiferon- TB, QTFG, Latent TB, IGRA

Specimen Collection

7.5 ml Lithium-heparin (Orange)

The lithium-heparin bottle must NOT contain any other components (gel or glass beads). The bottle must be filled to the maximum line.

Samples must be received by the lab no later than 16 hours post venesection.

Please note: Samples must be received in the laboratory from Monday-Thursday, between the hours of 08:00 and 16:00.

Turnaround time

14 Days

Test indications

This test is used to determine if a patient has been exposed to Mycobacterium tuberculosis (TB) by measuring a T-cell response to TB specific proteins. This test is recommended by NICE for the diagnosis of latent TB. Please refer to the following link for further guidance: https://www.nice.org.uk/guidance/ng33/chapter/Recommendations#preventing-tb

Indeterminate results can be found if the sample collection procedure is not strictly adhered to. Indeterminate results may also be found in patients with significant T-cell immune deficiency and those on long term immunosuppressive drugs.

Methodology

ELISA

Interferences

Anticoagulants other than lithium heparin. Excessive levels of circulating IFN-γ  or presence of heterophile antibodies

Reference Range

Analytical error

Contact the laboratory (x8454)

Reference change value

N/A