Quantiferon TB test

The FDA approved QuantiFERON®-TB Gold Plus assay tests for Cell Mediated Immune (CMI) responses to peptide antigens that simulate mycobacterial proteins. Individuals infected with M. tuberculosis complex organisms (M. tuberculosis, M. bovis, M. africanum, M. microti, M. canetti) typically have lymphocytes in their blood that recognize these and other mycobacterial antigens. This recognition process involves the generation and secretion of the cytokine, IFN-γ. The detection and subsequent quantification of IFN-γ forms the basis of this assay.

This test is for the diagnosis of latent TB (tuberculosis) infection, active TB disease requires AFB culture and smear, see AFBHSC.

This assay is reported as either:

• Evidence of Mycobacterium tuberculosis-specific memory T cell response. The Quantiferon-TB test cannot differentiate between latent tuberculosis infection (LTBI) and active tuberculosis infection. Clinical correlation advised.
• NO evidence of Mycobacterium tuberculosis-specific memory T cell response. Clinical correlation advised.

QuantiFERON®-TB Gold PLUS (4 tube assay):Collect 1 mL blood in each tube:

• Grey top (NIL) tube with SMALL CID QF-NIL label
• Green top (TB1 ANTIGEN) tube with SMALL CID QF-AG1 label
• Yellow top (TB2 ANTIGEN) tube with SMALL CID QF-AG2 label
• Purple top (MITOGEN) tube with SMALL CID QF-MIT label

The black mark on the side of tubes indicates the 1 mL fill volume. Do not under or over-fill. Immediately after filling tubes, shake all four tubes 10 times to ensure that the entire inner surface of the tube has been coated with the blood.

Tube Labeling Note: Please ONLY use SMALL LABELS and affix on tubes towards the top half so that there is a clear view of both the amount of blood in the tube and the manufacturer lot number.

After phlebotomy, the four QuantiFERON®-TB Gold PLUS tubes must be incubated within 16 hours of the blood draw and must arrive at the Virology lab within this timeframe. Once the blood has been drawn, hold all four tubes at room temperature until incubation.

The UW Virology Annex Central Lab is open from 07:00 to 21:00, and on holidays, from 08:00 to 17:00. If you are unable to contact Virology and are uncertain how to proceed, please call the Lab Medicine Resident at 206-598-6190.

Note: QuantiFERON® TB collection tubes are available in Lab Medicine's Specimen Processing. For UW-MT, call 206-598-6224; for HMC, call 206-744-3451. Store blood collection tubes at 4°C to 25°C prior to phlebotomy.

QuantiFERON®-TB Gold PLUS (4-tube assay): Verify that the volume in all four tubes is at or near the black fill mark. Use SMALL CID labels ONLY and place them near the top of the tube, ensuring that the black fill mark and the manufacturer lot number are not covered. Label as follows:

• Grey top (NIL) tube with SMALL CID QF-NIL label
• Green top (TB1 ANTIGEN) tube with SMALL CID QF-AG1 label
• Yellow top (TB2 ANTIGEN) tube with SMALL CID QF-AG2 label
• Purple top (MITOGEN) tube with SMALL CID QF-MIT label

Do not cover the blood volume level or the manufacturer lot number with labels.

Outside Laboratory: Call Client Support Services at 206-520-4600 to order supplies and coordinate specimen transport. Depending on the collection time and day of the week, the sample may need to be sent directly to the UW Virology Annex Central by courier to ensure it arrives within 16 hours. Alternatively, outside labs may incubate all four blood collection tubes upright at 37°C ± 1°C for 16 to 24 hours on-site. After incubation, mark the blood collection tubes as "INCUBATED." The Blood collection tubes may be held at 4°C to 27°C for up to 3 days after incubation and prior to centrifugation. Incubated tubes may also be centrifuged at 2000 to 3000 RCF (g) and held at 2°C to 8°C for up to 28 days. Please provide clear documentation of the 37°C incubation period on both the blood tubes and requisition.