The whole blood interferon-gamma assay (QuantiFERON-TB-2G; QFT) has not been fully evaluated as a baseline\r\ntuberculosis screening test in Japanese healthcare students commencing clinical contact. The aim of this study was to compare\r\nthe results from the QFT with those from the tuberculin skin test (TST) in a population deemed to be at a low risk for infection\r\nwith Mycobacterium tuberculosis. Methodology/Principal Findings. Healthcare students recruited at Okayama University\r\nreceived both the TST and the QFT to assess the level of agreement between these two tests. The interleukin-10 levels before\r\nand after exposure to M tuberculosis-specific antigens (early-secreted antigenic target 6-kDa protein [ESAT-6] and culture\r\nfiltrate protein 10 [CFP-10]) were also measured. Of the 536 healthcare students, most of whom had been vaccinated with\r\nbacillus-Calmette-Gue�´ rin (BCG), 207 (56%) were enrolled in this study. The agreement between the QFT and the TST results was\r\npoor, with positive result rates of 1.4% vs. 27.5%, respectively. A multivariate analysis also revealed that the induration\r\ndiameter of the TST was not affected by the interferon-gamma concentration after exposure to either of the antigens but was\r\ninfluenced by the number of BCG needle scars (p = 0.046). The whole blood interleukin-10 assay revealed that after antigen\r\nexposure, the median increases in interleukin-10 concentration was higher in the subgroup with the small increase in\r\ninterferon-gamma concentration than in the subgroup with the large increase in interferon-gamma concentration (0.3 vs. 0 pg/\r\nmL; p = 0.004). Conclusions/Significance. As a baseline screening test for low-risk Japanese healthcare students at their\r\ncourse entry, QFT yielded quite discordant results, compared with the TST, probably because of the low specificity of the TST\r\nresults in the BCG-vaccinated population. We also found, for the first time, that the change in the interleukin-10 level after\r\nexposure to specific antigens was inversely associated with that in the interferon-gamma level in a low-risk population.
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