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Free Content How to identify tuberculosis cases in a prevalence survey [Educational series: prevalence surveys. Serialised guidelines. Assessing tuberculosis prevalence through population-based surveys. Number 3 in the series]

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The identification of pulmonary tuberculosis (TB) cases in a prevalence survey is a challenge, as diagnostic methods are labour-intensive and large numbers of individuals need to be screened because the prevalence rate is low (almost never greater than 1200 per 100000 population). Three testing methods are used: questionnaires, chest radiography (CXR) and bacteriological tests, including sputum smear microscopy and culture. These methods can be applied in four strategies to identify cases. The most sensitive strategy is to apply all methods to each eligible individual. The next most sensitive option is to apply the questionnaire, CXR and sputum smear microscopy to each eligible individual and obtain sputum for culture from those individuals with symptoms, abnormalities on the CXR or a positive smear. If laboratory capacity is limited, screening using symptom enquiry and CXR can be used to select those individuals at highest risk of TB. These individuals are then requested to submit sputum for smear microscopy and culture. If neither CXR nor culture is available, sputum samples may be collected from all eligible individuals and examined by an enhanced microscopy method such as fluorescence microscopy. Case definitions are ideally based on the combined results of symptom enquiry, CXR and bacteriology.

Keywords: definition; guideline; prevalence; survey; tuberculosis

Document Type: Invited Paper

Affiliations: International Union Against Tuberculosis and Lung Disease, Paris, France

Publication date: November 1, 2008

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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