Mixed method estimation of population level HIV viral suppression rate in the Western Cape, South Africa

Introduction There are few population-wide data on viral suppression (VS) that can be used to monitor programmatic targets in sub-Saharan Africa. We describe how routinely collected viral load (VL) data from ART programmes can be extrapolated to estimate population VS and validate this using a combination of empiric and model-based estimates. Methods VL test results from were matched using a record linkage algorithm to obtain linked results for individuals. Test- and individual-level VS rates were based on test VL values <1000 cps/ml, and individual VL <1000 cps/mL in a calendar year, respectively. We calculated population VS among people living with HIV (PLWH) in the province by combining census-derived mid-year population estimates, HIV prevalence estimates and individual level VS estimates from routine VL data. Results Approximately 1.9 million VL test results between 2008 – 2018 were analysed. Among individuals in care, VS increased from 85.5% in 2008 to 90% in 2018. Population VS among all PLWH in the province increased from 12.2% in 2008 to 51.0% in 2017. The estimates derived from this method are comparable to those from other published studies. Sensitivity analyses showed that the results are robust to variations in linkage method, but sensitive to the extreme combinations of assumed ART coverage and population HIV prevalence. Conclusion While validation of this method in other settings is required, this approach provides a simple, robust method for estimating population VS using routine data from ART services that can be employed by national programmes in high-burden settings.