Screening of close contacts of pulmonary tuberculosis in an urban area in Shanghai, China: a cross-sectional study

OBJECTIVES: The study aimed to explore the risk factors of close contacts developing pulmonary tuberculosis (TB), identify active TB and describe the sociodemographic characteristics of active TB among close contacts in Putuo District, Shanghai. STUDY DESIGN: A cross-sectional study was conducted among the close contacts of pulmonary TB in Putuo District from 2017 to 2018. METHODS: Symptom questionnaire, Chest X-ray (CXR) and interferon-gamma release assay (IGRA) were carried out to screen the consenting close contacts. Three sputum samples were collected for sputum smear tests, sputum culture tests, and molecular-based diagnostics from whose screening was positive to confirm the diagnosis and receive treatment. RESULTS: A total of 1036 individuals were included in this study, with an average of 47.3 ± 19.4 years old, including 427 males and 609 females. Four of the close contacts had presumptive TB based on symptom screening. Fourteen had presumptive TB based on abnormal CXR finding and 52 had positive IGRA results. Multivariate analysis showed that index cases with positive sputum smears, close contacts who had presumptive TB based on symptom screening and their interaction term were at significantly higher risk of developing TB. CONCLUSIONS: Studies have shown particular emphasis should be put on those with bacteria-positive index cases or those who had presumptive TB based on symptom screening during follow-up. Since the proportion of latent tuberculosis infection is high among close contacts undergoing IGRA examination, measures such as tuberculosis preventive treatment can be considered to reduce the incidence of TB.