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Free Content Interferon-gamma release assays in immigrant contacts and effect of remote exposure to Mycobacterium tuberculosis

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Abstract:

OBJECTIVE: To assess the association between remote exposure to tuberculosis (TB) and results of the tuberculin skin test (TST), and two interferon-gamma release assays (IGRAs)—QuantiFERON®-TB Gold In-Tube (QFT-GIT) and T-SPOT.TB®—in immigrant contacts of sputum smear-positive TB patients.

METHODS: Immigrants aged ≥16 years in close contact with smear-positive TB patients were included. QFT-GIT and T-SPOT.TB were performed if the TST induration size was ≥5 mm. Associations between test results and origin from an endemic country were assessed.

RESULTS: Of 433 close contacts, 322 (74%) had TST ≥5 mm, of whom, 282 (88%) had valid test results for all assays. Positive QFT-GIT results were obtained for 152/282 (54%) and positive T-SPOT.TB for 168/282 (60%). After adjustment for age, sex and recent contact, positive IGRA results and TST results ≥10 mm were found to be more frequent among immigrants who originated from Africa, in particular sub-Saharan Africa.

CONCLUSION: When IGRAs are used to determine latent TB infection in foreign-born individuals, positive findings not only relate to recent TB infection, but also reflect prior TB exposure in the country of origin. This late reactivity will limit their usefulness in contact investigations among immigrants originating from endemic areas.

Keywords: IGRA; contact investigation; exposure; immigrants; tuberculin skin test

Document Type: Regular Paper

Affiliations: 1: KNCV Tuberculosis Foundation, The Hague, The Netherlands; Center for Infection and Immunity Amsterdam, Academic Medical Centre, Amsterdam, The Netherlands 2: Department of Infectious Diseases, Leiden University Medical Centre, Leiden, The Netherlands 3: Department of Tuberculosis Control, Municipal Health Service, Amsterdam, The Netherlands 4: KNCV Tuberculosis Foundation, The Hague, The Netherlands; and Center for Infection and Immunity Amsterdam, Academic Medical Centre, Amsterdam, The Netherlands 5: Department of Tuberculosis Control, Municipal Public Health Service Rotterdam-Rijnmond, Rotterdam, The Netherlands

Publication date: 2009-07-01

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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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