T-SPOT.TB interferon-g release assay performance in healthcare worker screening at nineteen U.S. Hospitals

Thomas C. King, Mark Upfal, Andrew Gottlieb, Philip Adamo, Edward Bernacki, Chris P. Kadlecek, Jeffrey G. Jones, Frances Humphrey-Carothers, Albert F. Rielly, Pamela Drewry, Kathy Murray, Marcie DeWitt, Janet Matsubara, Louis O'Dea, John Balser, Peter Wrighton-Smith

Research output: Contribution to journalArticlepeer-review

30 Scopus citations


Rationale: Interferon-g release assays have significant advantages over tuberculin skin testing in many clinical situations. However, recent studies have called into question their reliability in serial testing of healthcare workers because of reportedly high rates of positivity and high conversion/reversion rates on retesting. Objectives: To define the performance characteristics of the T-SPOT.TBtest, an interferon-γ release assay, during serial screening programs of healthcare workers at 19 U.S. hospitals. Methods: A total of 42,155 T-SPOT.TB test results from healthcare workers at 19 geographically diverse hospitals obtained for routine tuberculosis screening programs were analyzed to determine the rates of positivity, reversion, and conversion in serial testing data. Measurements and Main Results: In 19,630 evaluable serial pairs from 16,076 healthcare workers, the mean test positivity rate was 2.3% (range, 0.0-27.4%). The mean conversion rate was 0.8% (range, 0.0-2.5%), and the mean reversion rate was 17.6%. Positivity and conversion rates correlated with known tuberculosis risk factors including age and sex. The observed specificity of the T-SPOT.TB test was at least 98.6%. Conclusions: The high concordance and test completion rates in this study suggest that the T-SPOT.TB test is a reliable tool for healthcare worker serial screening. As expected, the observed positivity rates were lower compared with the tuberculin skin test, likely reflecting the higher specificity of this test. Furthermore, the observed rates of conversion were low and significantly correlated with the geographic incidence of tuberculosis. Our findings suggest that the T-SPOT.TB test is an accurate and reliable way to screen healthcare workers.

Original languageEnglish (US)
Pages (from-to)367-373
Number of pages7
JournalAmerican journal of respiratory and critical care medicine
Issue number3
StatePublished - Aug 1 2015


  • Conversion
  • LTBI
  • Reversion
  • Serial testing
  • Tuberculosis screening

ASJC Scopus subject areas

  • Pulmonary and Respiratory Medicine
  • Critical Care and Intensive Care Medicine


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