title: A prospective longitudinal study evaluating a T-cell-based assay for latent tuberculosis infection in health-care workers in a general hospital in Beijing.
abstract: BACKGROUND
  The health-care workers (HCWs) are at high risk of acquiring infection with Mycobacterium tuberculosis. The objectives of this study were to compare the performance of the T-SPOT.TB and tuberculin skin test (TST) for latent tuberculosis infection (LTBI), evaluate diagnostic concordance and risk factors for LTBI, and observe the progression to active tuberculosis (TB) disease among HCWs in a general hospital in Beijing.
  
  
  METHODS
  The prospective cohort study enrolled HCWs in a tertiary general hospital in Beijing, China, to evaluate LTBI with T-SPOT.TB and TST. The subjects were evaluated every 12 months during the 60-month follow-up.
  
  
  RESULTS
  Of 101 participating HCWs, 96 and 101 had valid TST and T-SPOT.TB results, respectively. Twenty-nine (28.7%, 95% confidence interval (CI), 19.9% - 37.5%) were defined as positive by T-SPOT.TB and 53 (55.2%, 95%CI, 45.2% - 64.9%) were defined as positive by TST (using a ≥ 10 mm cutoff). An agreement between the two tests was poor (57.3%, κ = 0.18, 95%CI, 0.01% - 0.52%). In multivariate analysis, direct exposure to sputum smear-positive TB patients was a significant risk factor for a positive T-SPOT.TB (OR 5.76; 95%CI 1.38 - 24.00). Pooled frequency of antigen-specific IFN-γ secreting T-cells for subjects who reported direct contact with sputum smear-positive TB patients was significantly higher than that for participants without direct contact (P = 0.045). One of 20 participants with positive result of T-SPOT.TB and TST developed active TB at 24-month follow-up.
  
  
  CONCLUSIONS
  T-SPOT.TB is a more accurate, targeted method of diagnosing LTBI than TST.
authors.affiliation: Department of Infectious Diseases, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, China.
authors.forename: Li-fan
authors.initials: LF
authors.lastname: Zhang
authors.forename: Xiao-qing
authors.initials: XQ
authors.lastname: Liu
authors.forename: Yao
authors.initials: Y
authors.lastname: Zhang
authors.forename: Guo-hua
authors.initials: GH
authors.lastname: Deng
authors.forename: Manish
authors.initials: M
authors.lastname: Pareek
authors.forename: Ajit
authors.initials: A
authors.lastname: Lalvani
mesh_terms: D000328:Adult; D005260:Female; D006282:Health Personnel; D006769:Hospitals, General; D006801:Humans; D055985:Latent Tuberculosis / Q000175:diagnosis* / Q000209:etiology / Q000276:immunology; D008137:Longitudinal Studies; D008297:Male; D010865:Pilot Projects; D011446:Prospective Studies; D012307:Risk Factors; D014374:Tuberculin Test