Risk of tuberculosis (TB) disease in immigrants referred for post-landing TB medical surveillance: A retrospective cohort study in British Columbia, Canada

Background: People identified as high-risk of tuberculosis (TB) disease during the Immigration Medical Examination (IME) are referred to provincial programs for post-landing TB surveillance.Factors contributing to TB risk in this population are not well understood.Objectives: To assess the association between clinical and demographic factors documented during the IME and the diagnosis of TB disease within two years of arrival among people referred for post-landing surveillance in British Columbia (BC), Canada.Methods: A retrospective cohort study of 2,895 participants referred for post-landing surveillance in BC was conducted between January 1, 2020 and December 31, 2022.Cox proportional hazards regression was used to identify risk factors for TB disease, with participants followed for two years from their IME referral.Results: Abnormal chest x-ray findings were the factor most strongly associated with TB disease, present in 96.8% of those diagnosed.Participants with abnormal chest x-ray and those from high TB incidence countries had significantly higher hazards of developing TB disease, with adjusted hazard ratios of 9.14 and 4.82, respectively.Conclusion: Chest x-ray abnormalities and TB incidence in the country of origin are strongly associated with TB disease.Post-landing surveillance efforts should prioritize individuals with radiographic abnormalities and those from high-incidence countries.