QUANTIFERON-TB ASSAY

Collect  5 mL of whole blood into a 6 mL blood collection tube containing Lithium-Heparin as the anticoagulant.   

Alternately, collect a minimum of 3mL of whole blood into each of the two 4 mL Lithium-Heparin blood collection tubes.

Lithium Heparin tube (dark green cap)  

5 mL in single 6 mL blood collection tube containing Lithium-Heparin as the anticoagulant.

Alternately, 3 mL of whole blood into each of the two 4 mL Lithium-Heparin blood collection tubes.

Transport to the laboratory refrigerated.

Collect whole blood directly into a Lithium-Heparin blood collection tube (minimum volume 5 mL) and gently mix by inverting the tube several times to dissolve the heparin.

Alternately, collect whole blood directly into two Lithium-Heparin blood collection tube (minimum volume 3 mL into each) and gently mix by inverting the tubes several times to dissolve the heparin.

Collect by venipuncture only - DO NOT collect via line. 

Important:  Lithium-Heparin tube should be at room temperature (17-25 degrees Centigrade) at the time of blood collection.

Blood drawn into Lithium-Heparin tube must be held at room temperature (17-25 degrees Centigrade) for 15 minutes.  Transport to the laboratory refrigerated (2-8 degrees Centigrade).

Lithium-Heparin tube must not remain at room temperature for more than 3 hours after collection.  Refrigerate specimens during transport. Refrigerated specimen must be received into the laboratory within 48 hours from time of collection.

Underfilled Lithium-Heparin tube (below 5 mL) or (below 3mL in each). Refrigerated Lithium-Heparin tube received in lab after 48 hours from the time of collection.  Lithium-Heparin tube not refrigerated within 3 hours of collection. Specimen container unlabeled or labeled incorrectly. No date/time of collection or collector completed.

3 - 5 days

Interferon gamma release assay (ELISA)

Clinical Microbiology Laboratory

QFT, QFT Plus

QFT Gold Plus 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 diagnositic evaluations.

86480

The QuantiFERON^R TB Gold Plus (in Tube) assay is intended for use as an aid in diagnosis of TB infection. 

A qualitative result (i.e., Negative, Positive, or Indeterminate) is based on interpretation of the four values, Nil, TB1 minus Nil, TB2 minus Nil, and Mitogen minus Nil. The Nil value represents nonspecific reactivity produced by the patient specimen. The TB1 minus Nil value indicates the interferon-gamma response of CD4+ T lymphocytes, specifically stimulated by the TB1 antigens. The TB2 minus Nil value indicates interferon-gamma response of both CD4+ and CD8+ T lymphocytes, stimulated by the TB2 antigens. The Mitogen minus Nil value serves as the positive control, demonstrating the successful responsiveness of the T lymphocytes in patient specimen.

A negative result suggests that M. tuberculosis infection is unlikely. However, in patients with high suspicion of exposure, a negative test should be repeated on a new sample.

A positive result indicates an interferon-gamma response to M. tuberculosis antigens, suggesting infection with M. tuberculosis.

Positive result in patients at low-rick for tuberculosis should be interpreted with caution and repeat testing on a new sample is advised. If repeat testing is positive, treatment may be indicated. Consult Infectious Disease Services for further recommendations.

False positive results may occur in patients with prior infection with M. marinum, M. szulgai, and M. kansasii.

For an indeterminate result, the likelihood of determining infection with M. tuberculosis cannot be determined. If clinically indicated, repeat testing on a new sample is advised.

For further information, refer to http://www.cdc.gov/mmwr/pdf/rr/rr5905.pdf and  https://doi.org/10.1093/cid/ciw694.