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Free Content Risk of tuberculosis among contacts of isoniazid-resistant and isoniazid-susceptible cases

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OBJECTIVE: To compare the risk to household contacts of isoniazid (INH) susceptible and INH-resistant cases of tuberculosis (TB) in a rural community in South India.

METHODS: In all, 5562 contacts of INH-susceptible and 779 contacts of INH-resistant patients and 246 845 persons with no TB case in the home were followed for 15 years, with surveys every 2.5 years comprising radiographic and sputum examination, selective follow-up of high-risk individuals and passive surveillance. If a new case developed, the household members were assigned to the ‘INH-susceptible’ (n = 7088) or ‘INH-resistant’ series (n = 526), whichever appropriate. Logistic regression and Cox's proportional hazards model were employed.

RESULTS: The baseline prevalence of tuberculous infection was respectively 70% and 56% in contacts of INH-resistant and INH-susceptible patients (P < 0.001), compared to 46% in non-contacts. The incidence of culture-positive TB was respectively 295 and 311 per 100 000, compared to 162/100 000 in non-contacts. The adjusted hazard ratios were 2.4 and 2.0 for contacts of INH-resistant and INH-susceptible patients.

CONCLUSION: The baseline prevalence of tuberculous infection was substantially higher in contacts of INH-resistant than INH-susceptible patients, but the incidence of tuberculous disease over a 15-year follow-up was similar in the two series, and twice as high as in non-contacts.

Keywords: INH-resistant TB; contacts; hazard ratios; infectivity; risk

Document Type: Regular Paper


Publication date: 2011-06-01

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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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