Completeness of preventive therapy for tuberculosis in indigenous versus nonindigenous populations in the Brazilian Amazon: a retrospective cohort study

Background Tuberculosis preventive therapy (TPT) is crucial for preventing the progression from TB infection (TBI) to active disease, particularly among vulnerable populations such as indigenous people. Although shorter regimens have improved adherence, evidence from real-world programmatic settings is limited. This study evaluated whether the indigenous race was associated with greater TPT completion in the Brazilian Amazon. Methods We conducted a retrospective cohort study using data from the IL-TB database (2019–2023) in Amazonas, Brazil. Individuals who initiated TPT were stratified by race. The primary outcome was TPT completion. Multivariate logistic regression identified factors associated with completion, adjusting for sociodemographic, clinical, and operational variables. Results Of the 4,887 individuals, 79.6% completed TPT. Completion was higher among Indigenous individuals (90.9%) than among Nonindigenous individuals (79.1%) (p < 0.001). In the adjusted analysis, indigenous race (OR: 2.4; 95% CI: 1.49–4.06), shortened TPT regimens (OR: 2.36; 95% CI: 2.04–2.73), and receiving care in noncapital municipalities (OR: 2.03; 95% CI: 1.49–2.82) were positively associated with completion. Foreign nationality (OR: 0.28; 95% CI: 0.18–0.44) and TPT nonexclusive primary health care services (OR: 0.79; 95% CI: 0.66–0.94) were negatively associated with such outcomes. Among nonindigenous individuals, associations mirrored those in the overall population. Among Indigenous individuals, only a shortened regimen was significantly associated with completion (OR: 5.75; 95% CI: 1.78–23.4). Conclusions Indigenous individuals presented greater TPT completion, particularly when treated with shortened regimens. These findings reinforce the potential of decentralized strategies and the use of shortened regimens to increase the completeness of tuberculosis preventive therapy and provide evidence for overcoming historical and operational barriers at the program level that still prevail and delay the improvement of public policies aimed at achieving global TB elimination goals, especially in high-burden settings, social inequality and the strong presence of vulnerable populations.