Risk of Active Tuberculosis among Index Case of Householders-A Long-Term Assessment after the Conventional Contacts Study

Objectives: The aim of this study was to determine the incidence of active tuberculosis (TB) among household contacts of TB-index cases diagnosed during a 7-year period in a public Primary Care Center located in a high-incidence area.

Design and sample: A retrospective cohort study was performed. Data collection was based on the capture-recapture method; the two main sources crossed information from TB-index and contact cases from the El Fondo Primary Care Center (Santa Coloma de Gramenet, Spain) and their reports to the National Epidemiologic Surveillance Service.

Measures: Variables were divided into demographic and health data (result of the Mantoux test, chest X-ray, presence of risk factors, and indication for chemoprophylaxis).

Results: Community nurses identified 103 household contacts that underwent the conventional contact study. Overall, 60.19% were male; the mean age was 29.08 years. Only one case of secondary active TB was found, representing an incidence of 0.56% per TB-index case and year.

Conclusion: The incidence of new secondary TB among household contacts with TB-index cases was of a case. Nevertheless, a long-term follow-up of these householders beyond the conventional contacts study should be considered in areas with higher incidences of TB or among specific high-risk populations.