Abstract

Abstract:

BACKGROUND:

Clinical data with use of serial interferon release assay (IGRA) testing in US health care workers (HCWs) is limited.

METHODS:

This is a single center, retrospective chart review of health care workers (HCWs) from 2007-2010, who underwent pre-employment testing with QuantiFERON-TB Gold In-Tube™ (QFT-GIT). Demographic data, BCG history, prior TST result if done, baseline and serial IGRA values of the HCWs were obtained. The number of IGRA converters and reverters and their subsequent management by Infectious Disease (ID) physicians were reviewed. Quantitative IGRA negative values were not available.

RESULTS:

7374 IGRAs were performed on newly hired HCWs. Of these, 486 (6.6%) were positive at baseline, 305 (4.1%) were indeterminate, and 6583 (89.3%) were negative. During 2007-2010, 52 (2.8%) of 1857 HCWs 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.

CONCLUSIONS:

Clinical significance of most QFT-GIT conversions in serial testing remains a challenging task for clinicians. The use of single cut-off point criteria for IGRA may lead to over diagnosis of new TB infections. Clinical assessment and evaluation may help prevent unnecessary therapy in these cases. The criteria for defining conversions and reversions by establishing new cut-offs needs to be further evaluated, especially in HCWs.