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Free Content Prevalence and trends of infection with Mycobacterium tuberculosis in Djibouti, testing an alternative method

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SETTING: Djibouti, 1994 and 2001.

OBJECTIVE: To estimate the prevalence of tuberculosis (TB) and average annual risk of TB infection (ARTI) and trends, and to test a new method for calculations.

METHODS: Tuberculin surveys among schoolchildren and sputum smear-positive TB patients. Prevalence of infection was calculated using cut-off points, the mirror image technique, mixture analysis, and a new method based on the operating characteristics of the tuberculin test. Test sensitivity was derived from tuberculin reactions among TB patients and test specificity from a comparison of reaction size distributions among children with and without a BCG scar.

RESULTS: The ARTI was estimated to lie between 2.6% and 3.1%, with no significant changes between 1994 and 2001. The close match of the distributions between children tested in 1994 and patients justifies the utilisation of the latter to determine test sensitivity. This new method gave very consistent estimates of prevalence of infection for any induration for values between 15 and 20 mm. Specificity was successfully determined for 1994, but not for 2001. Mixture analysis confirmed the estimates obtained with the new method.

CONCLUSION: Djibouti has a high ARTI, and no apparent change over the observation time was found. Using operating test characteristics to estimate prevalence of infection looks promising.

Keywords: Djibouti; mixture analysis; risk of infection; test operating characteristics; tuberculosis

Document Type: Regular Paper

Affiliations: 1: Tuberculosis Division, International Union Against Tuberculosis and Lung Disease, Paris, France 2: Independent Consultant, Antony, France 3: National Tuberculosis Programme, Djibouti, Republic of Djibouti 4: Independent Consultant, Laguiole, France 5: Independent Consultant, Cénon, France

Publication date: October 1, 2005

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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