Green top tube (sodium heparin)
Do NOT centrifuge! Keep at room temperature (18-22°C).
Preferred volume: 10 mL
Minimum volume: 6 mL
Frozen, clotted, hemolyzed, spun down, citrate anticoagulant (blue top)
Maintain and transport specimens at room temperature (18-22°C).
Ship specimens Priority Overnight via Fed Ex in container sufficiently insulated to avoid temperature extremes (<10°C and >37°C).
24 hours at room temperature (18-22°C).
Samples must arrive within 24 hours of draw and are accepted Monday through noon on Friday.
Immunology Lab - Functional Assay
t spot;IGRA;T-Spot (Tuberculosis Interferon Gamma Release Assay)
Quantiferon TB Test (QTB)
The T-SPOT.TB test is based on the measurement of a cell mediated response to Mycobacterium tuberculosis-specific antigens (ESAT-6 and CFP-10). Peripheral blood mononuclear cells (PBMC) are separated from whole blood and incubated in plates coated with anti-interferon gamma (IFNg) antibodies with these antigens for 16-24 hours. Following incubation, IFNg-producing cells are detected using a second anti- IFNg antibody, an enzyme linked conjugate, and substrate. Controls include unstimulated cells (Nil control) and phytohemagglutinin stimulated cells (Mitogen control). A test is considered positive or borderline when IFNg- spot forming units (SFU) produced in response to either of the TB antigens is significantly greater than the Nil control (TB-Nil; positive = > 8 SFU, borderline = 5, 6 or 7 SFU), and the Mitogen control has a robust IFNg response. The T-Spot.TB result is indeterminate if the Nil control is high (>10 SFU) or the mitogen control is low (< 20 SFU). Although the test is reported qualitatively, IFNg SFU for the individual test conditions are also reported as recommended by the Centers for Disease Control and Prevention1.
The T-Spot.TB detects infections due to M. tuberculosis complex (M. tuberculosis, M. bovis and M. africanum). BCG strains and nontuberculous mycobacteria with the exception of M. marinum, M. kansasii, M. szulgai and M. gordonae do not express ESAT-6 and CFP-10 proteins. Therefore, patients either vaccinated with BCG or infected with most nontuberculous mycobacterial strains should test negative.
T-Spot.TB results should always be interpreted in conjunction with clinical and other relevant laboratory findings.
1 Guidelines for Using the QuantiFERON®-TB Gold Test for Detecting Mycobacterium tuberculosis Infection, United States. Centers for Disease Control and Prevention. Morbidity and Mortality Weekly Report (MMWR). December 16, 2005 / 54(RR15);49-55