title: Whole blood interferon-gamma assay for baseline tuberculosis screening among Japanese healthcare students.
abstract: BACKGROUND
  The whole blood interferon-gamma assay (QuantiFERON-TB-2G; QFT) has not been fully evaluated as a baseline tuberculosis screening test in Japanese healthcare students commencing clinical contact. The aim of this study was to compare the results from the QFT with those from the tuberculin skin test (TST) in a population deemed to be at a low risk for infection with Mycobacterium tuberculosis.
  
  
  RESULTS
  Healthcare students recruited at Okayama University received both the TST and the QFT to assess the level of agreement between these two tests. The interleukin-10 levels before and after exposure to M tuberculosis-specific antigens (early-secreted antigenic target 6-kDa protein [ESAT-6] and culture filtrate protein 10 [CFP-10]) were also measured. Of the 536 healthcare students, most of whom had been vaccinated with bacillus-Calmette-Guérin (BCG), 207 (56%) were enrolled in this study. The agreement between the QFT and the TST results was poor, with positive result rates of 1.4% vs. 27.5%, respectively. A multivariate analysis also revealed that the induration diameter of the TST was not affected by the interferon-gamma concentration after exposure to either of the antigens but was influenced by the number of BCG needle scars (p = 0.046). The whole blood interleukin-10 assay revealed that after antigen exposure, the median increases in interleukin-10 concentration was higher in the subgroup with the small increase in interferon-gamma concentration than in the subgroup with the large increase in interferon-gamma concentration (0.3 vs. 0 pg/mL; p = 0.004).
  
  
  CONCLUSIONS
  As a baseline screening test for low-risk Japanese healthcare students at their course entry, QFT yielded quite discordant results, compared with the TST, probably because of the low specificity of the TST results in the BCG-vaccinated population. We also found, for the first time, that the change in the interleukin-10 level after exposure to specific antigens was inversely associated with that in the interferon-gamma level in a low-risk population.
authors.affiliation: Health and Environmental Center, Okayama University, Okayama, Japan. khotta@md.okayama-u.ac.jp
authors.forename: Katsuyuki
authors.initials: K
authors.lastname: Hotta
authors.forename: Toshio
authors.initials: T
authors.lastname: Ogura
authors.forename: Kenji
authors.initials: K
authors.lastname: Nishii
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Kodani
authors.forename: Masaru
authors.initials: M
authors.lastname: Onishi
authors.forename: Yukito
authors.initials: Y
authors.lastname: Shimizu
authors.forename: Arihiko
authors.initials: A
authors.lastname: Kanehiro
authors.forename: Katsuyuki
authors.initials: K
authors.lastname: Kiura
authors.forename: Mitsune
authors.initials: M
authors.lastname: Tanimoto
authors.forename: Kazuo
authors.initials: K
authors.lastname: Tobe
mesh_terms: D000293:Adolescent; D000328:Adult; D006801:Humans; D007371:Interferon-gamma / Q000097:blood*; D008297:Male; D008403:Mass Screening; D009169:Mycobacterium tuberculosis / Q000276:immunology / Q000472:pathogenicity; D014374:Tuberculin Test; D014376:Tuberculosis / Q000175:diagnosis* / Q000453:epidemiology / Q000276:immunology
chemical_list: D007371:Interferon-gamma