title: Tuberculosis infection in drug users: interferon-gamma release assay performance.
abstract: METHODS
  An inner city neighborhood in Houston, Texas, known for a high rate of drug use.
  
  
  OBJECTIVE
  To determine the prevalence of latent tuberculosis infection (LTBI) using the QuantiFERON-TB Gold (QFT-G) test, the TSPOT.TB test and the tuberculin skin test (TST) in drug users and to evaluate the performance of the QFT-G and TSPOT.TB tests vs. the TST.
  
  
  METHODS
  Cross-sectional study. Bivariate and multivariate logistic regression analyses were used to determine risks associated with each test outcome.
  
  
  RESULTS
  The prevalence of LTBI in 119 drug users studied was 28% by TST and 34% by QFT-G and T-SPOT.TB. Kappa statistics indicated fair to moderate concordance between QFT-G and TSPOT.TB vs. TST. About one-fifth of the population that tested negative with TST was positive with either QFT-G or T-SPOT.TB. On multivariate analysis, the likelihood of testing QFT-positive or T-SPOT.TB-positive increased by 8% and 6%, respectively, for every year of age; TST positivity was associated with smoking crack at home; being Caucasian or having a history of alcohol use was positively associated with a positive T-SPOT.TB test.
  
  
  CONCLUSIONS
  Interferon-gamma release assays (IGRAs) are superior to the TST in drug users with a higher prevalence of LTBI. Future studies need to assess the predictive value of IGRAs on the progression from LTBI to active TB in high-risk populations.
authors.affiliation: University of Texas Health Science Center at Houston, School of Public Health, Houston, TX, USA.
authors.forename: C Z
authors.initials: CZ
authors.lastname: Grimes
authors.forename: L-Y
authors.initials: LY
authors.lastname: Hwang
authors.forename: M L
authors.initials: ML
authors.lastname: Williams
authors.forename: C M
authors.initials: CM
authors.lastname: Austin
authors.forename: E A
authors.initials: EA
authors.lastname: Graviss
mesh_terms: D000293:Adolescent; D000328:Adult; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D007371:Interferon-gamma / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D019966:Substance-Related Disorders / Q000150:complications*; D014376:Tuberculosis / Q000150:complications / Q000175:diagnosis*
chemical_list: D007371:Interferon-gamma