Clinical data: T-SPOT.TB test performance

Clinical studies

King, TC, Upfa M, et al. T-SPOT.TB Interferon-γ Release Assay Performance in Healthcare Worker Screening at Nineteen U.S. Hospitals. American Journal of Respiratory and Critical Care Medicine, Vol. 192, No. 3 (2015), pp. 367-373. doi: 10.1164/rccm.201501 0199OC.

This landmark study of over 42,000 serial tests from 19 geographically diverse US hospitals demonstrates the performance of the T-SPOT.TB test. 

Key findings in this paper include:

• 98.9% concordance rate
• 0.8% mean conversion rate (negative result converting to a positive result)
• 17.6% mean reversion rate (positive result converting to a negative result)
• T-SPOT.TB results are strongly correlated to known tuberculosis (TB) risk factors
• This study demonstrated the T-SPOT.TB test is a reliable tool for healthcare worker screening

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Screening health care workers with interferon-γ release assay versus tuberculin skin test: Impact on costs and adherence to testing (the SWITCH study)

Bernacki E, Humphrey F, Sneed L, Tao X, Wrighton-Smith P. “Screening health care workers with interferon-γ release assay versus tuberculin skin test: impact on costs and adherence to testing (the SWITCH study).” J Occup Environ Med. 2012 Jul;54(7):806-15. doi: 10.1097/JOM.0b013e318254620f.

This landmark study is the first-of-its-kind to analyze the actual cost of a TB surveillance program using the tuberculin skin test (TST) or the T-SPOT.TB test by obtaining direct measurements of all program components.

Key findings in this paper include:

• The study exposes the false economics of the TST, demonstrating that it actually costs $73.20 per test to perform when accounting for all components of a TST screening program
• A test price of $54.83 or lower for the T-SPOT.TB test is more cost-effective than the TST
• T-SPOT.TB compliance was 99%; increasing the TST compliance to 98.5% would cost an additional $20.59 per employee

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Tuberculosis antigen-specific immune responses can be detected using enzyme-linked immunospot technology in human immunodeficiency virus (HIV)-1 patients with advanced disease

Clark SA, Martin SL, Pozniak A, et al. Tuberculosis antigen-specific immune responses can be detected using enzyme-linked immunospot technology in human immunodeficiency virus (HIV)-1 patients with advanced disease. Clin Exp Immunol. 2007;150(2):238–244. doi:10.1111/j.1365-2249.2007.03477.x

This study evaluated whether it is possible to detect TB antigen-specific immune responses using ELISPOT technology in HIV-1 patients – a hard to screen patient population.

A key finding in this study includes:

• The sensitivity of the T-SPOT.TB test remains high in HIV patients, regardless of CD4 T cell count

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Utility of the T-SPOT.TB test’s borderline category to increase test resolution for results around the cut-off point

Rego, K, Pereira K, et al. Utility of the T-SPOT.TB test’s borderline category to increase test resolution for results around the cut-off point. Tuberculosis. 2018;108:178-185. doi.org/10.1016/j.tube.2017.12.005.

This paper analyzed over 645,000 T-SPOT.TB tests to examine the utility of the borderline zone.

Key findings from this study include:

• Patients who received borderline results could have been inappropriately classified if using a single cut-off point test with no borderline category
• The FDA-approved T-SPOT.TB test borderline zone provided increased test resolution around the test cut-off point
• Invalid rate of 0.6% in a study of > 645,000 tests

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Diagnostic performance of whole-blood interferon-γ assay and enzyme-linked immunospot assay for active tuberculosis

Lai CC, Tan CK,et al. Diagnostic performance of whole-blood interferon-γ assay and enzyme-linked immunospot assay for active tuberculosis. J Microbiol Immunol Infect. 2011 Oct;44(5):406-7. doi: 10.1016/j.jmii.2011.07.002. Epub 2011 Sep 8.

This study compared the diagnostic performance of two interferon-gamma release assays in patients with suspected active TB.

Key findings from this study include:

• The T-SPOT.TB test had less false negative results, especially in immunocompromised patients, compared to the other commercially available IGRA
• The T-SPOT.TB test had a higher sensitivity than the other commercially available IGRA

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Tuberculosis Screening of New Hospital Employees Compliance, Clearance to Work Time, and Cost Using Tuberculin Skin Test and Interferon-Gamma Release Assays

Foster-Chang, SA DNP, APRN-BC, COHN-S; Manning, ML PhD, CRNP, CIC, FAAN; et al. Tuberculosis Screening of New Hospital Employees Compliance, Clearance to Work Time, and Cost Using Tuberculin Skin Test and Interferon-Gamma Release Assays. Workplace Health & Safety. 2014 Sep:62(11): 460-467 doi.org/10.3928/21650799-20140902-02

This study examines the administrative, logistic and technical ease of use of an interferon-gamma release assay (IGRA) compared to the tuberculin skin test (TST) when screening new hired healthcare personnel.

Key findings in this study include:

• The average time to clear new employees to start work decreased from 13.18 days to 5.91 days when the institution used an IGRA instead of the TST
• TB screening costs were reduced by 38% – 40% when institutions utilized  an IGRA
• Selection of the most suitable TB test should be based on purpose, setting, effectiveness and cost

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T-SPOT.TB package insert

The T-SPOT.TB test is an in vitro diagnostic test for the detection of effector T cells that respond to stimulation by Mycobacterium tuberculosis antigens ESAT-6 and CFP10 by capturing interferon-gamma (IFN-γ) in the vicinity of T cells in human whole blood collected in heparin blood collection tube. It is intended for use as an aid in the diagnosis of M. tuberculosis infection.