Zheng, AmyFox, Matthew P.Greener, RossKileel, Emma M.Bor, JacobVenter, Willem Daniel FrancoisPisa, Pedro TerrenceBrennan, Alana T.Maskew, Mhairi2026-01-222026-01-222025-06Zheng, A., Fox, M.P., Greener, R. et al. 2025, 'Initiation of Dolutegravir versus Efavirenz on viral suppression and retention at 6 months : a regression discontinuity design', JAIDS Journal of Acquired Immune Deficiency Syndromes, vol. 99, no. 2pp. 151-157. DOI: 10.1097/QAI.0000000000003642.1525-4135 (print)1077-9450 (online)10.1097/QAI.0000000000003642http://hdl.handle.net/2263/107509BACKGROUND : In 2019, South Africa's Antiretroviral Therapy (ART) Treatment Guidelines replaced efavirenz with dolutegravir in first-line ART. SETTING : We assessed the impact of this national guideline change on retention and viral suppression in the Themba Lethu Clinical Cohort, Johannesburg, South Africa. We applied a regression discontinuity design in a prospective cohort study of 1654 adults living with HIV initiating first-line ART within 12 months (±12 months) of the guideline change. METHODS : We compared outcomes in individuals presenting just before and after the guideline change and estimated intention-to-treat effects on initiating a dolutegravir- vs efavirenz-based regimen. Primary outcomes were retention and viral suppression. Participants were defined as retained in care if a visit took place within ±3 months of the 6-month end point. Viral suppression was defined as having a viral load ≤1000 copies/mL 3 months before and up to 6 months after the 6-month end point. RESULTS : The 2019 guideline change led to an increase in uptake of dolutegravir. We noted a 26.6 percentage point increase in the proportion initiating dolutegravir [95% Confidence Interval (CI): 14.1 to 38.6]. We saw a small increase in viral suppression [Risk Difference (RD): 7.4 percentage points; 95% CI: -1.6 to 16.5] and no change in retention (RD: -1.7 percentage points; 95% CI: -13.9 to 10.5) at 6 months, though our findings were imprecise. CONCLUSIONS : Our estimates suggest early uptake of the revised treatment guidelines after implementation. Despite this, there was no meaningful change in viral suppression and retention rates at 6 months.en© 2025 The Author(s). This is an open access article distributed under the Creative Commons Attribution License 4.0 (CCBY).HIV/AIDSAntiretroviral therapy (ART)RetentionSuppressionSouth AfricaHuman immunodeficiency virus (HIV)Acquired immune deficiency syndrome (AIDS)DolutegravirEfavirenzArticle