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Free Content Analysis of the frequency distribution of tuberculin skin test readings: a tool for the assessment of group contact investigations

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SETTING: The public health tuberculosis control program covering Seattle, Washington, and its surrounding suburban areas.

OBJECTIVE: To describe a tool of potential usefulness in the assessment of transmission of tuberculosis in contact investigations of groups, such as co-workers or schoolmates of an infectious case, with a low prior probability of latent tuberculosis infection (LTBI).

DESIGN: Tuberculin skin test (TST) readings in mm of the group being tested were graphed and compared with the known frequency distributions of TST readings of populations with and without LTBI, the latter including a fraction with non-specific tuberculin reactivity.

RESULTS: Four group contact investigations were analyzed retrospectively with this tool. In two the graphed TST readings of contacts fell within the distribution of a population with LTBI, and suggested that transmission had occurred. In the other two, the graphed readings better fit the distribution of a population with non-specific tuberculin reactivity and suggested that transmission had not occurred.

CONCLUSION: This simple tool to facilitate the determination of whether transmission of tuberculosis has occurred, and who should be offered treatment for LTBI in contact investigations of groups of people, deserves further study.

Keywords: latent tuberculosis infection; tuberculin skin test; tuberculosis

Document Type: Regular Paper

Affiliations: Tuberculosis Control Program, Department of Public Health, Seattle and King County, Seattle, Washington, USA

Publication date: December 1, 2003

More about this publication?
  • 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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