Risk of active tuberculosis in adult household contacts of smear-positive pulmonary tuberculosis cases.

SETTING: Seven public tuberculosis (TB) dispensaries in Istanbul, Turkey.

OBJECTIVE: To investigate the risk of active TB among adult household contacts (age > or = 15 years) of newly diagnosed sputum smear-positive pulmonary TB (PTB) cases in Istanbul.

DESIGN: A retrospective analysis of adult household contacts of 1570 pulmonary TB cases registered at seven TB dispensaries in Istanbul between 1997 and 2000.

RESULTS: A total of 6188 household contacts (mean contact/index case: 3.9) were included in the study, of whom 4114 (67%) were aged > or = 15 years (mean contact/index case: 2.6); 3310 (80.5%) of these participated in a contact investigation. The mean duration of follow-up was 2.2 years (range 1-4 years); 222 active TB cases (rate 5.4%, 95%CI 5.2-5.6) were detected, 171 within the first year. The incidence of active TB was 2491/100 000 (3555/100 000 in the 15-34 year age group and 1195/100 000 in the > or = 35 year age group, P < 0.0001). Rates of active TB were highest in the 15-24 year (8.5%) and 25-34 year (6.5%) age groups.

CONCLUSION: The incidence of active TB among adult household contacts of sputum smear-positive PTB cases was high. This high incidence justifies the prescription of chemopropylaxis not only for children but also for all contacts, especially those aged between 15 and 34 years.