Tuberculosis infection in drug users: interferon-gamma release assay performance

Int J Tuberc Lung Dis. 2007 Nov;11(11):1183-9.


Setting: 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.

Design: 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.

Conclusion: 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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Enzyme-Linked Immunosorbent Assay
  • Female
  • Humans
  • Interferon-gamma / metabolism*
  • Male
  • Middle Aged
  • Substance-Related Disorders / complications*
  • Tuberculosis / complications
  • Tuberculosis / diagnosis*


  • Interferon-gamma