Questionable effectiveness of the QuantiFERON-TB gold test (cellestis) as a screening tool in healthcare workers

OBJECTIVE. The Center for Disease Control and Prevention recommends the use of QuantiFERON TB Gold test (QFTG; Cellestis) in all situations where the tuberculin skin test (TST) is used. In November 2007, our institution replaced its screening-tool TST with the QFTG in-tube assay (QFT-GIT) for annual screening of latent tuberculosis infection among healthcare workers (HCWs). This study evaluated the effectiveness of QFT-GIT test as screening tool in HCWs at our institution. METHODS. This retrospective study reviewed medical records of all HCWs who underwent screening with QFT-GIT from January 2008 through December 2008. RESULTS. Among the 6,530 HCWs screened with QFT-GIT from January through December 2008, 287 had a positive test result. Of the 287, 123 had positive TST results in the past, meaning that 164 HCWs had newly diagnosed latent tuberculosis infection by QFT-GIT. Of the 164 HCWs, 135 were retested by QFT-GIT and were simultaneously tested with TST within 4 weeks after the initial QFT-GIT. Of these 135 HCWs, 66 reverted to negative results and results remained positive for 69 with QFT-GIT. Only 2 HCWs had a positive TST result. CONCLUSIONS. The disagreement between QFT-GIT and TST results and the high reversion rate with QFT-GIT raise concerns about the effectiveness of QFT-GIT as a sole screening test in HCWs.