Exploring engagement with antiretroviral care for people living with HIV in a high burden setting in South Africa

Sustaining individual and public health benefits of antiretroviral programmes requires long-term maintenance of treatment success, making support for lifelong, optimal engagement with HIV care a priority. This thesis explored longitudinal patterns of engagement to contribute to the growing understanding of the complexity of engagement behaviour, particularly in lower-resource settings. I developed a framework to define engagement and its composite dimensions: retention (engagement with services), adherence (engagement with treatment) and active self-management (owning engagement to sustain treatment success). To explore retention, I applied a selection of the measures of engagement identified in a scoping study, to a cohort of 68888 adults on treatment in two low-resource, high-burden settings in South Africa. Using routine health data, suboptimal retention was shown to drive low rates of population-level viral suppression. Survival analysis and group-based trajectory modelling revealed that treatment interruptions were common, patterns were similar after initiation and restart, disengagement was heterogenous, and subgroups of engagement trajectories were strongly associated with treatment outcomes, even when adjusted for potential confounders. A subset of the population was optimally engaged over time, with high rates of viral suppression despite frequent short interruptions. Baseline clinical and demographic factors were only weakly predictive of retention, and most with an interruption were low-risk individuals. These insights into the dynamic and heterogenous nature of long-term engagement complement cross-sectional cascade findings, particularly engagement patterns after restart. The results support recommendations to measure different engagement dimensions and use treatment interruptions to assess retention. Interruptions appear a ‘normal’ part of lifelong engagement with HIV care, requiring a shift in the intervention approach to manage interruptions as expected. Considering present difficulties predicting disengagement, subgroups of engagement behaviour in routine data could facilitate the application of precision public health principles to monitor HIV services and target resources efficiently, informing the next phase of the epidemic response.