Abstract
BACKGROUND: We evaluated tuberculosis (TB) acquisition rate and risk factors among health care workers (HCWs) exposed to index TB patients. METHODS: We performed a retrospective cohort study on exposed HCWs from August 2016 to January 2018 at a tertiary hospital in Singapore. Demographic factors and TB exposure episodes per HCW were obtained. A modified Poisson regression model was used to identify factors associated with TB infection. RESULTS: A total of 32 TB exposure events occurred during the study period. A total of 881 HCWs with 1,536 exposure episodes were screened with QuantiFERON-TB Gold In-tube assay (QFT-GIT) at baseline and 8 weeks. A total of 129 (14.6%) HCWs had positive QFT-TB at baseline, whereas 22 (2.5%) HCWs had QFT-GIT conversion, with a latent TB infection (LTBI) rate of 1.14 cases per 100 exposure episodes per year. Foreign nationality, non-Chinese ethnicity, and age above 40 years were independently associated with baseline LTBI, whereas having >2 TB exposure episodes and working in internal medicine, medical subspecialties, and psychiatry wards were associated with QFT-GIT conversion. DISCUSSION: The QFT-GIT conversion rate among screened HCWs is low. Foreign HCWs with LTBI likely came from countries with higher TB transmission. Targeted prevention of repeated TB exposures can reduce QFT-GIT conversion. CONCLUSIONS: The study results will guide TB contact tracing protocols in health care institutions.