| Summary: | Abstract Background Tuberculosis (TB) remains a major cause of avoidable deaths. Economic migrants represent a vulnerable population due to their exposure to medical and social risk factors. These factors expose them to higher risks for TB incidence and poor treatment outcomes. Methods This cross-sectional study evaluated WHO-defined TB treatment outcomes among economic migrants in an urban district of Ho Chi Minh City, Viet Nam. We measured the association of a patient’s government-defined residency status with treatment success and loss to follow-up categories at baseline and performed a comparative interrupted time series (ITS) analysis to assess the impact of community-based adherence support on treatment outcomes. Key measures of interest of the ITS were the differences in step change (β6) and post-intervention trend (β7). Results Short-term, inter-province migrants experienced lower treatment success (aRR = 0.95 [95% CI: 0.92–0.99], p = 0.010) and higher loss to follow-up (aOR = 1.98 [95% CI: 1.44–2.72], p < 0.001) than permanent residents. Intra-province migrants were similarly more likely to be lost to follow-up (aOR = 1.86 [95% CI: 1.03–3.36], p = 0.041). There was evidence that patients > 55 years of age (aRR = 0.93 [95% CI: 0.89–0.96], p < 0.001), relapse patients (aRR = 0.89 [95% CI: 0.84–0.94], p < 0.001), and retreatment patients (aRR = 0.62 [95% CI: 0.52–0.75], p < 0.001) had lower treatment success rates. TB/HIV co-infection was also associated with lower treatment success (aRR = 0.77 [95% CI: 0.73–0.82], p < 0.001) and higher loss to follow-up (aOR = 2.18 [95% CI: 1.55–3.06], p < 0.001). The provision of treatment adherence support increased treatment success (IRR(β6) = 1.07 [95% CI: 1.00, 1.15], p = 0.041) and reduced loss to follow-up (IRR(β6) = 0.17 [95% CI: 0.04, 0.69], p = 0.013) in the intervention districts. Loss to follow-up continued to decline throughout the post-implementation period (IRR(β7) = 0.90 [95% CI: 0.83, 0.98], p = 0.019). Conclusions Economic migrants, particularly those crossing provincial borders, have higher risk of poor treatment outcomes and should be prioritized for tailored adherence support. In light of accelerating urbanization in many regions of Asia, implementation trials are needed to inform evidence-based design of strategies for this vulnerable population.
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