How soon should patients be eligible for differentiated service delivery models for antiretroviral treatment? Evidence from Zambia

IntroductionAttrition from HIV treatment is high during patients first 6 months after antiretroviral therapy (ART) initiation and patients with less than 6 months on ART are systematically excluded from most differentiated service delivery (DSD) models, which are intended to reduce attrition. Despite eligibility criteria requiring greater than 6 months on ART, some patients enroll earlier. Using routinely-collected medical record data in Zambia, we compared loss to follow-up (LTFU) among patients enrolling in DSD models early (<6 months on ART) to LTFU among those who enrolled according to guidelines ([&ge;]6 months on ART) in order to assess whether the ART experience eligibility criterion is necessary. MethodsWe extracted data from electronic medical records for adults ([&ge;]15 years) who initiated ART between 01/01/2019 and 31/12/2019 and evaluated LTFU, defined as >90 days late for last scheduled medication pickup, at 18 months for "early enrollers" (DSD enrolment after <6 months on ART) and "established enrollers" (DSD enrolment after [&ge;]6 months on ART). We used a log-binomial model to compare LTFU risk between groups, adjusting for age, sex, urban/rural status, ART refill interval and DSD model. ResultsFor 6,340 early enrollers and 25,857 established enrollers there were no important differences between the groups in sex (61% female), age (median 37 years), or setting (65% urban). ART refill intervals were longer for established vs early enrollers (72% vs 55% were given 4-6-month refills). LTFU at 18 months was 3% (192/6,340) for early enrollers and 5% (24,646/25,857) for established enrollers. Early enrollers were 41% less likely to be LTFU than established patients (adjusted risk ratio [95% confidence interval] 0.59 [0.50-0.68]). ConclusionsPatients enrolled in DSD models in Zambia with < 6 months on ART were more likely to be retained in care than patients referred after they were established on ART. A limitation of the analysis is that early enrollers may have been selected for DSD participation due to providers and patients expectations about future retention. Offering DSD model entry to at least some ART patients <6 months after ART initiation may help address high attrition during the early treatment period.