title: Detection of Mycobacterium tuberculosis infection in United States Navy recruits using the tuberculin skin test or whole-blood interferon-gamma release assays.
abstract: BACKGROUND
  Military personnel are at risk for acquiring Mycobacterium tuberculosis infection because of activities in close quarters and in regions with a high prevalence of tuberculosis (TB). Accurate tests are needed to avoid unnecessary treatment because of false-positive results and to avoid TB because of false-negative results and failure to diagnose and treat M. tuberculosis infection. We sought to estimate the specificity of the tuberculin skin test (TST) and 2 whole-blood interferon-gamma release assays (QuantiFERON-TB assay [QFT] and QuantiFERON-TB Gold assay [QFT-G]) and to identify factors associated with test discordance.
  
  
  METHODS
  A cross-sectional comparison study was performed in which 856 US Navy recruits were tested for M. tuberculosis infection using the TST, QFT, and QFT-G.
  
  
  RESULTS
  Among the study subjects, 5.1% of TSTs resulted in an induration > or = 10 mm, and 2.9% of TSTs resulted in an induration > or = 15 mm. Eleven percent of QFT results and 0.6% of QFT-G results were positive. Assuming recruits at low risk for M. tuberculosis exposure were not infected, estimates of TST specificity were 99.1% (95% confidence interval [CI], 98.3%-99.9%) when a 15-mm cutoff value was used and 98.4% (95% CI, 97.3%-99.4%) when a 10-mm cutoff value was used. The estimated QFT specificity was 92.3% (95% CI, 90.0%-94.5%), and the estimated QFT-G specificity was 99.8% (95% CI, 99.5%-100%). Recruits who were born in countries with a high prevalence of TB were 26-40 times more likely to have discordant results involving a positive TST result and a negative QFT-G result than were recruits born in countries with a low prevalence of TB. Nineteen (50%) of 38 recruits with this type of discordant results had a TST induration > or = 15 mm.
  
  
  CONCLUSIONS
  The QFT-G and TST are more specific than the QFT. No statistically significant difference in specificity between the QFT-G and TST was found using a 15-mm induration cutoff value. The discordant results observed among recruits with increased risk of M. tuberculosis infection may have been because of lower TST specificity or lower QFT-G sensitivity. Negative QFT-G results for recruits born in countries where TB is highly prevalent and whose TST induration was > or = 15 mm suggest that the QFT-G may be less sensitive than the TST. Additional studies are needed to determine the risk of TB when TST and QFT-G results are discordant.
authors.affiliation: Division of Tuberculosis Elimination, Centers for Disease Control and Prevention, Atlanta, GA 30333, USA. gym6@cdc.gov
authors.forename: Gerald H
authors.initials: GH
authors.lastname: Mazurek
authors.forename: Margan J
authors.initials: MJ
authors.lastname: Zajdowicz
authors.forename: Arlene L
authors.initials: AL
authors.lastname: Hankinson
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Costigan
authors.forename: Sean R
authors.initials: SR
authors.lastname: Toney
authors.forename: James S
authors.initials: JS
authors.lastname: Rothel
authors.forename: Laura J
authors.initials: LJ
authors.lastname: Daniels
authors.forename: F Brian
authors.initials: FB
authors.lastname: Pascual
authors.forename: Nong
authors.initials: N
authors.lastname: Shang
authors.forename: Lisa W
authors.initials: LW
authors.lastname: Keep
authors.forename: Philip A
authors.initials: PA
authors.lastname: LoBue
mesh_terms: D000293:Adolescent; D000328:Adult; D015331:Cohort Studies; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D007371:Interferon-gamma / Q000097:blood*; D008297:Male; D008889:Military Personnel; D009326:Naval Medicine; D011933:Reagent Kits, Diagnostic; D012680:Sensitivity and Specificity; D014374:Tuberculin Test; D014376:Tuberculosis / Q000175:diagnosis* / Q000208:ethnology / Q000276:immunology*