Impact of Viral Load Monitoring on Retention and Viral Suppression: A Regression Discontinuity Analysis of South Africa's National Laboratory Cohort.

When human immunodeficiency virus (HIV) viral loads exceed 1,000 copies/mL, South African guidelines recommend repeat viral load testing within 6-months. We assessed whether South African facilities follow viral load monitoring guidelines and whether guidelines improve HIV-related outcomes using a regression discontinuity design in a national HIV cohort of 174,574 patients (2013-2015). We assessed whether patients with viral loads just above versus just below 1,000 copies/mL were more likely to receive repeat testing in 6-months, and compared differences in clinic transfers, retention, and viral suppression. The majority (67%) of patients with viral loads >1,000 copies/mL did not receive repeat testing within 6 months, and these patients were 8.0% (95% CI: 6.2%, 9.7%) more likely to receive repeat testing compared to ≤1,000 copies/mL. Eligibility for repeat testing (>1,000 copies/mL) was associated with greater 12-month retention (Risk Difference (RD): 2.9% [95% CI: 0.6%, 5.2%]), and combined suppression and retention (RD: 5.8% [95% CI: 3.0%, 8.6%]). Patients with viral loads >1,000 copies/mL who actually received repeat testing were 85.2% more likely to be both retained and suppressed at 12-months (95% CI: 35.9%, 100.0%). Viral load monitoring may improve patient outcomes, but most patients with elevated viral loads do not receive monitoring within recommended timelines.