The impact of differentiated service delivery (DSD) on retention in care and viral suppression in South Africa: A target trial emulation of routine care data

Introduction Replacing conventional, facility-based HIV treatment with less intensive differentiated service delivery (DSD) models could benefit DSD clients and the health system, but its value depends on maintaining or improving clinical outcomes. We compared retention and viral suppression between antiretroviral therapy (ART) clients enrolled in DSD models to those eligible for but not enrolled in DSD models in South Africa. Methods We applied a target trial emulation (TTE) methodology to data from South Africa’s electronic medical record system (TIER.Net) for 18 clinics across 3 provinces and estimated retention in care (attended clinic visit within 12 months) and viral suppression (<400 copies/ml3) at 12, 24, and 36 months after follow-up start date, defined as DSD enrollment date for the intervention arm and the first trial enrollment period clinic visit for the comparison arm. Clients were eligible for DSD models if they were ≥18 years old, on ART ≥12 months, and had two suppressed viral load (VL) measurements, per prevailing national guidelines. For the TTE, we designated eight 6-month target trial enrolment periods between 1 July 2017 and 1 July 2021. For each period, we estimated the risk differences for retention in care and viral suppression by comparing those enrolled in DSD models to those not enrolled, using a Poisson distribution with an identity link function. We report adjusted and unadjusted risk differences for clients enrolled in DSD models and for DSD-eligible clients not enrolled in a DSD model. Results and discussion 49,595 unique individuals were eligible for DSD enrolment over eight target trials, contributing to a total of 148,943 trial-clients, of whom 17% (25,775) were enrolled in DSD models. The pooled adjusted risk difference for retention in care between clients enrolled in DSD and those not enrolled in DSD was 3.2% (95% confidence interval (CI) 1.6%; 4.7%) at 12 months, 4.2% (2.4%; 6.0%) at 24 months, and 4.4% (2.0%; 6.8%) at 36 months. For viral suppression, the adjusted risk difference comparing DSD to non-DSD was estimated to be 1.4% (-0.5%; 3.2%) at 12 months, 1.7% (-0.5%; 4.0%) at 24 months, and 1.4% (-0.6%; 4.4%) at 36 months. Results remained consistent across target trials. Clients who were younger, lived in urban settings, or had less ART experience at trial enrolment had lower retention.  Conclusions Clients enrolled in DSD models in South Africa had slightly better retention in care and similar viral suppression to those who were eligible for but not enrolled in DSD. With better or equivalent outcomes, DSD models can be assessed on the basis of non-clinic costs and benefits, such as changes in quality of care and resource utilization.