Free Content Concordance of a positive tuberculin skin test and an interferon gamma release assay in bacille Calmette-Guérin vaccinated persons

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BACKGROUND: False-positive tuberculin skin test (TST) results due to prior bacille Calmette-Guérin (BCG) vaccination may lead to unnecessary treatment of presumed latent tuberculosis infection (LTBI). Recently approved interferon-gamma release assays (IGRAs) are more specific for LTBI in this group.

METHODS: A total of 316 BCG-vaccinated foreign-born individuals with a positive TST had a commercially available IGRA (QuantiFERON®-TB Gold In-Tube) performed as part of a two-step procedure to determine the need for isoniazid therapy. Baseline demographic information and TST size were recorded and analyzed for characteristics associated with an increased likelihood of having a positive IGRA.

RESULTS: Increasing age, male sex, origin from a country with a high prevalence of tuberculosis (TB), shorter time since arrival in the United States, and increasing TST size were all independently associated with a positive IGRA.

CONCLUSION: Patient characteristics and TST size can help determine those at highest risk for LTBI. A two-step procedure for LTBI screening should be considered for foreign-born persons with prior BCG vaccination and a positive TST.

Keywords: BCG; LTBI; PPD; interferon-gamma release assay; tuberculosis

Document Type: Regular Paper

Affiliations: 1: Department of Medicine, MetroHealth Medical Center, Cleveland, Ohio, USA 2: Tuberculosis Research Unit, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA

Publication date: February 1, 2011

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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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