Tuberculosis infection among close contacts of patients with pulmonary tuberculosis in China: a population-based, multicentered study

Objectives Limited information is currently available on the prevalence of and risk factors for tuberculosis infection (TBI) among close contacts of pulmonary TB (PTB) patients in China. In this study, we estimated the burden of TBI among close contacts using QuantiFERON-TB Gold In-Tube (QFT) and identified factors associated with TB transmission among this high-risk population. Methods Between January 1 2018 and August 31 2020, we identified laboratory-confirmed PTB patients from a population-based, multicentered, cluster-randomized control trial for tuberculosis preventive treatment (TPT). Close contacts of these patients were identified, interviewed and tested using QFT. We estimated TBI prevalence and calculated odds ratios (ORs) and 95% confidence intervals (CIs) for TBI risk factors. Results A total of 3,138 index cases and 8,117 close contacts were identified. Of these contacts, 36 contacts had PTB (prevalence of 443.51 cases/100,000 population). Among the remaining 7,986 close-contacts, 3,124 (39.12%) had a positive QFT result. QFT positivity was significantly associated with older age [adjusted OR: 1.77 (95% CI 1.27-2.47), 2.20 (95% CI 1.59-3.05) and 2.74 (95% CI 1.96-3.82) for the age groups of "35-44", "45-54" and "55-64" respectively, compared with the age group "5-14"], longer contact duration (adjusted OR 1.44; 95% CI 1.22-1.69), and sharing bedroom (adjusted OR 1.39; 95% CI 1.18-1.65). Conclusions Our findings indicate a high TBI burden among the close contacts of PTB. The results also highlighted that contacts tracing and investigation for TBI are necessary and beneficial, particularly for those who are older, have longer contact duration – including sharing a bedroom.