Predictors of the observed high prevalence of loss to follow-up in ART-experienced adult PLHIV: a retrospective longitudinal cohort study in the Tanga Region, Tanzania.

Background: Antiretroviral therapy (ART) programs have expanded rapidly, and they are now accessible free of charge, yet "loss to follow-up, LTFU" is still a national public health issue. LTFU may result in treatment failure, hospitalization, increased risk of opportunistic infections and drug-resistant strains, and shortening the quality of life. This study described the rates and predictors of LTFU among adults living with human immunodeficiency virus (PLHIV) on ART in the Tanga region, Tanzania.

Methods: A retrospective longitudinal cohort study was conducted between October 2018 and December 2020 in Tanga's care and treatment health services facilities. The participants were HIV adult PLHIV aged 15 years and above on ART and attended the clinic at least once after ART initiation. LTFU was defined as not taking ART refills for 3 months or beyond from the last attendance of a refill and not yet classified as dead or transferred out. Cox proportional hazard regression models were employed to identify risk factors for LTFU. P values were two-sided, and we considered a p < 0.05 statistically significant.

Results: 57,173 adult PLHIV were on ART of them, 15,111 (26.43%) were LTFU, of whom 10,394 (68.78%) were females, and 4717 (31.22%) were males. Factors independently associated with LTFU involved age between 15 and 19 years (HR: 1.85, 95% CI 1.66-2.07), male sex (HR: 2.00 95% CI 1.51-2.62), divorce (HR: 1.35, 95% CI 1.24-1.48), second-line drug type (HR: 1.13, 95% CI 1.09-1.18), poor drug adherence (HR: 1.50, 95% CI 1.23-1.75), unsuppressed viral load (HR: 2.15, 95% CI 2.02-2.29), not on DTG-related drug (HR: 7.51, 95% CI 5.88-10.79), advanced HIV disease WHO stage III and IV (HR: 2.51, 95% CI 2.32-2.72). In contrast to cohabiting, ART duration < 1 year, and being pregnant showed a reduced likelihood of LTFU.

Conclusion: A high prevalence of LTFU was observed in this study. Young age, not using DTG-based regimen, WHO clinical stage IV, poor drug adherence, male sex, unsuppressed viral load, divorcee, and second-line regime were independently associated with LTFU. To reduce LTFU, evidence-based interventions targeting the identified risk factors should be employed.