• Kimberlee S Fong, J Walton Tomford, Lucileia Teixeira, Thomas G Fraser, David van Duin, Belinda Yen-Lieberman, Steve M Gordon, and Cyndee Miranda.
• Department of Infectious Disease, Cleveland Clinic, Cleveland, OH 44195, USA. fongk2@ccf.org
• Chest. 2012 Jul 1;142(1):55-62.

BackgroundClinical data with use of serial interferon-γ release assay (IGRA) testing in US health-care workers (HCWs) are limited.MethodsA single-center, retrospective chart review was done from 2007 to 2010 of HCWs who underwent preemployment QuantiFERON-TB Gold In-Tube testing. Demographic data, bacille Calmette-Guérin history, prior tuberculin skin test result if done, and baseline and serial IGRA values were obtained. The number of IGRA converters and reverters and their subsequent management by infectious disease physicians were reviewed. Quantitative IGRA-negative values were not available.ResultsA total of 7,374 IGRAs were performed on newly hired HCWs. Of these tests, 486 (6.6%) were positive at baseline, 305 (4.1%) were indeterminate, and 6,583 (89.3%) were negative. From 2007 to 2010, 52 of 1,857 HCWs (2.8%) with serial IGRA tests were identified as converters, with a serial IGRA median value of 0.63 IU/mL. Seventy-one percent of HCWs with IGRA conversion had values ≤ 1 IU/mL. None of the converters had active TB or were part of an outbreak investigation.ConclusionsClinical significance of most QuantiFERON-TB Gold In-Tube conversions in serial testing remains a challenging task for clinicians. The use of a single cutoff point criterion for IGRA may lead to overdiagnosis of new TB infections. Clinical assessment and evaluation may help to prevent unnecessary therapy in these cases. The criteria for defining conversions and reversions by establishing new cutoffs needs to be evaluated further, especially in HCWs.

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