Serial QuantiFERON TB-2G Testing Over a Four-year Period in Healthcare Workers at a City Hospital

Abstract

Objective To evaluate the performance and practicality of QuantiFERON TB-2G (QFT-2G) testing for screening healthcare workers (HCWs) at a city hospital in Japan without a tuberculosis (TB)-specific ward.
Methods We performed a chart review of 951 HCWs (251 men and 700 women) who underwent QFT-2G testing as a part of their pre-employment or annual employee screening between April 2007 and March 2010.
Results The initial QFT-2G test was interpreted as positive in 28 (2.9%) HCWs, negative in 884 HCWs (92.9%) and indeterminate in 39 HCWs (4.1%). During the four-year study period, 37 HCWs were diagnosed as being positive at least once. Nine (0.98%) of the 923 HCWs with indeterminate or negative results on the initial testing converted to a positive status, including 6/479 (1.25%) nurses, 2/100 (2.0%) office staff members and 1/147 (0.68%) physicians. No HCWs with a positive result had a history of tuberculosis (TB) or any apparent contact with active TB patients and did not opt for treatment of latent TB. Seven (25%) of the 28 HCWs who were determined to be positive on the initial testing reverted to an indeterminate or negative status.
Conclusion In a series of annual serial QFT-2G tests, some HCWs exhibited conversion and/or reversion. Therefore, caution is required when interpreting mild fluctuations in interferon-γ responses.