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

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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.

Keywords: crack cocaine; interferon-gamma release assay; tuberculin skin test; tuberculosis

Document Type: Regular Paper

Affiliations: 1: University of Texas Health Science Center at Houston, School of Public Health, Houston, Texas, USA 2: Department of Pathology, Baylor College of Medicine, Houston, Texas, USA

Publication date: November 1, 2007

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  • The International Journal of Tuberculosis and Lung Disease publishes articles on all aspects of lung health, including public health-related issues such as training programmes, cost-benefit analysis, legislation, epidemiology, intervention studies and health systems research. The IJTLD is dedicated to the continuing education of physicians and health personnel and the dissemination of information on tuberculosis and lung health world-wide.

    Certain IJTLD articles are selected for translation into French, Spanish, Chinese or Russian. They are available on the Union website

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