Performance of a Score to Characterize Adequate Contact among the Social Network of Persons with Tuberculosis

Abstract

Background. Exposure to an individual with tuberculosis is necessary for transmission to occur. Previously, we developed a score that measures contact between tuberculosis cases and their social networks in an African urban context. This score was built using exploratory factor analysis and identified contact as the conjunction of two domains – setting and relationship. Now, our aim is to determine whether this score covaries with the presence of tuberculous infection among social contacts of tuberculosis cases.Methods. This was a large cross-sectional study conducted in Kampala, Uganda from 2012-2016. Tuberculous infection was assessed in social contacts of adult tuberculosis cases. We estimated the prevalence of tuberculous infection in this population, overall and according to the setting and relationship domains. We calculated the prevalence ratio (PR) for the association between increasing scores in the setting and relationship domains and tuberculous infection, adjusted by other covariates, using modified Poisson regression models. Results. We enrolled 955 household and community contacts from 119 tuberculosis cases. The overall prevalence of tuberculous infection in the social networks was 52% (95% confidence interval [CI], 48-55). The prevalence of tuberculous infection in very low, low, medium, and high setting-contact quartiles was 44%, 40%, 53%, and 70% respectively (Ptrend<.0001). By the relationship score, the prevalence of tuberculous infection in very low, low, moderate and high-contact groups was 41%, 47%, 53% and 66% respectively (Ptrend<.0001). The effect of the setting score in the prevalence of tuberculous infection was higher among children between 5-14 years (PR=1.26; 95% CI 1.15-1.39) whereas the relationship score was associated with tuberculous infection in children of 0-4 years (PR=1.42; 95% CI 1.10-1.82)Conclusion. In this large observational study from an urban African setting, participants, especially children, with higher setting and relationship scores were more likely infected with Mycobacterium tuberculosis among contacts of a tuberculosis case.