Geographic variation in loss to follow-up from HIV care in Tanzania and its association with pharmacy refill adherence in routine programme data

BackgroundSustained retention in HIV care is essential for achieving durable viral suppression and controlling the HIV epidemic. Loss to follow-up (LTFU) remains a persistent challenge in sub-Saharan Africa and shows substantial geographic variation. However, nationally representative analyses of routine monitoring data remain limited. Pharmacy refill data provide a scalable and objective approach for identifying individuals at risk of disengaging from care. We assessed the magnitude, spatial distribution, and predictors of LTFU among people living with HIV (PLHIV) receiving antiretroviral therapy (ART) across 26 mainland regions of Tanzania. MethodsWe conducted a retrospective cohort analysis using routinely collected program data from the National Care and Treatment Clinic (CTC-2) database of PLHIV receiving ART in Tanzania between 2017 and 2021. LTFU was defined as no recorded clinic visit for [&ge;]180 days after the last scheduled appointment, consistent with monitoring definitions used by the National AIDS and Sexually Transmitted Infections Control Programme (NASHCoP). Pharmacy refill adherence was calculated longitudinally and categorized as good ([&ge;]85%) or poor (<85%). Regional and district-level patterns were visualized using geospatial mapping. Multivariable logistic regression models were used to identify predictors of LTFU. ResultsA total of 52,828 PLHIV were included in the study, representing all 26 mainland regions of Tanzania. Overall, 26.6% were classified as LTFU during follow-up, with marked regional variation. The highest proportional LTFU was observed in Dar es Salaam (33.2%), followed by Njombe (32.9%) and Geita (32.7%), while the lowest was recorded in Mwanza (19.1%) and Iringa (20.3%). Good pharmacy refill adherence ([&ge;]85%) was strongly associated with lower odds of LTFU and remained the most robust independent predictor after adjustment (adjusted odds ratio [aOR] 0.34; 95% confidence interval [CI] 0.32-0.35). District-level analyses revealed substantial within-region heterogeneity, identifying localized clusters of elevated attrition not apparent in regional aggregates. ConclusionLTFU remains a major challenge to sustaining effective ART delivery in Tanzania. Pharmacy refill adherence may serve as a practical early indicator for identifying individuals at risk of disengagement from HIV care. Integrating refill-based monitoring with spatially informed analysis may support targeted retention strategies within routine HIV treatment programs.