Treatment eligibility and retention in clinical HIV care: A regression discontinuity study in South Africa

Background: loss to follow-up is high among hiv patients not yet receiving antiretroviral therapy (art). clinical trials have demonstrated the clinical efficacy of early art; however,these trials may miss an important real-world consequence of providing art at diagnosis: its impact on retention in care. methods and findings: we examined the effect of immediate (versus deferred) art on retention in care using a regression discontinuity design. the analysis included all patients (n = 11,306) entering clinical hiv care with a first cd4 count between 12 august 2011 and 31 december 2012 in a public-sector hiv care and treatment program in rural south africa. patients were assigned to immediate versus deferred art eligibility,as determined by a cd4 count < 350 cells/μl,per south african national guidelines. patients referred to pre-art care were instructed to return every 6 months for cd4 monitoring. patients initiated on art were instructed to return at 6 and 12 months post-initiation and annually thereafter for cd4 and viral load monitoring. we assessed retention in hiv care at 12 months,as measured by the presence of a clinic visit,lab test,or art initiation 6 to 18 months after initial cd4 test. differences in retention between patients presenting with cd4 counts just above versus just below the 350-cells/μl threshold were estimated using local linear regression models with a data-driven bandwidth and with the algorithm for selecting the bandwidth chosen ex ante. among patients with cd4 counts close to the 350-cells/μl threshold,having an art-eligible cd4 count (<350 cells/μl) was associated with higher 12-month retention than not having an art-eligible cd4 count (50% versus 32%),an intention-to-treat risk difference of 18 percentage points (95% ci 11 to 23; p < 0.001). the decision to start art was determined by cd4 count for one in four patients (25%) presenting close to the eligibility threshold (95% ci 20% to 31%; p < 0.001). in this subpopulation,having an art-eligible cd4 count was associated with higher 12-month retention than not having an art-eligible cd4 count (91% versus 21%),a complier causal risk difference of 70 percentage points (95% ci 42 to 98; p < 0.001). the major limitations of the study are the potential for limited generalizability,the potential for outcome misclassification,and the absence of data on longer-term health outcomes. conclusions: patients who were eligible for immediate art had dramatically higher retention in hiv care than patients who just missed the cd4-count eligibility cutoff. the clinical and population health benefits of offering immediate art regardless of cd4 count may be larger than suggested by clinical trials. © 2017 bor et al.