Exploring the validity of routine individuated service data for antenatal HIV surveillance in the Western Cape.

Background: Monitoring progress of HIV programmes is reliant on robust surveillance. The WHO Consolidated guidelines on person-centred HIV strategic information recommend moving towards using routine programmatic data for HIV surveillance rather than seroprevalence surveys which are costly and inefficient. In the Western Cape province of South Africa, public-sector individual-level routine data from various sources are linked on a unified platform through the Provincial Health Data Centre (PHDC). This allows monitoring of provincial antenatal HIV seroprevalence over time. We assessed the validity of these routine individuated data compared to aggregated program data and population-wide sentinel antenatal HIV seroprevalence surveys for the Western Cape.

Methods: We conducted a retrospective cohort analysis of pregnancies identified in the PHDC from January 2011 to December 2020. Unique identifiers were used to link antenatal and HIV care records from routine electronic systems. HIV prevalence estimates were compared with available antenatal seroprevalence survey estimates and register-based aggregate program data from the District Health Information System. Provincial, district-level and age-group HIV prevalence estimates were compared between data systems using correlation coefficients, absolute differences and trend analysis.

Results: Of the 977,800 pregnancies ascertained, PHDC HIV prevalence estimates from 2011 to 2013 were widely disparate from aggregate and survey data (due to incomplete electronic data), whereas from 2014 onwards, estimates were within the 95% confidence interval of survey estimates, and closely correlated to aggregate data estimates (r = 0.8; p = 0.01), with an average prevalence difference of 0.4%. PHDC data show a slow but steady increase in provincial HIV prevalence from 16.7% in 2015 to 18.6% in 2020. The highest HIV prevalence was in the Cape Metro district (20.3%) Prevalence estimates by age group were comparable between sentinel surveys and PHDC from 2015 onwards, with prevalence estimates stable over time among younger age-groups (15-24 years) but increased among older age-groups (> 34 years).

Conclusions: This study compares sentinel seroprevalence surveys with both routine register-based aggregate data and individuated data. Based on recent estimates, we show that in this setting linked individuated data may be reliably used for HIV prevalence surveillance and provide more granular estimates with improved efficiency compared to seroprevalence surveys and register-based aggregate data.