Tuberculosis Interferon Gamma Release Assay
Test Code
TSPOT
Description
T-SPOT.TB is an in vitro diagnostic test to detect if a patient has an immunological response to Mycobacterium tuberculosis. It is intended for use as an aid in the diagnosis of M. tuberculosis infection. This test evaluates the number of T cells that respond to stimulation (detected by interferon-gamma production) and provides a measurement of the abundance of M. tuberculosis sensitive effector T cells in the peripheral blood.
Collect
Collect whole blood in sodium heparin tube (Green top).
Preferred volume: 10 mL.
Patient Prep
Do NOT centrifuge!Keep at room temperature (18-22°C).
Pediatric Collection
Minimum volume: 6 mL
Unacceptable Conditions
Frozen, clotted, hemolyzed, spun down, citrate anticoagulant (blue top)
Storage Transport Temp
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).
Stability
24 hours at room temperature (18-22°C).
Notes
Samples must arrive within 24 hours of draw and are accepted Monday through noon on Friday.
Performed
Tuesday - Friday
Methodology
Elispot
Turnaround Time
48 hours
Department
Immunology Lab - Functional Assay
Synonyms
TSPOT.TB, IGRA, tspot, t spot, T-Spot, Tuberculosis Interferon Gamma Release Assay
Study Offerings
CAP/CLIA
Ordering Recommendations
Recommended for people who are at increased risk of developing TB disease, such as those who:Have been in close contact with someone with active TB
Live in a high-risk area for TB
Have been diagnosed with LTBI in the past
For tuberculosis disease (i.e. active TB), please see AFB2c or NAAT
If you are sending more than 10 patient samples, ADx Client Services must be called at 800.550.6227 to schedule testing before sample is shipped. Please indicate the number of specimens you anticipate sending in your call.
Related Tests
QuantiFERON® -TB Gold Plus In-Tube, QFT4
Reference Interval
Negative
Interpretation
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 invalid 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
CPT Code
86481
New York Approved
FDA Approved or Cleared
FDA
Approved or Cleared