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

Abstract

Most differentiated service delivery (DSD) models for HIV treatment, which are intended to improve ART programme outcomes, require that a patient have spent ≥6 or ≥12 months on antiretroviral treatment (ART) ART for eligibility. Attrition from ART programmes, however, is highest among those newly initiated and thus ineligible for DSD models. Because some patients are enrolled “early,” prior to 6 or 12 months on ART, we were able to evaluate loss to follow-up among patients in Zambia enrolled in DSD models after differing intervals on ART.Data were extracted from electronic medical records of patients (≥15 years) enrolled in DSD models from October 2019-March 2020. We compared 12-month loss to follow-up (LTFU), defined as “lost to follow-up,” “inactive,” or “stopped ART” at 9-15 months after DSD enrolment, among patients enrolled in six DSD models after <6 months, 6-12 months, and ≥ 12 months on ART, with those enrolled with <6 or <12 months on ART termed “early enrollers and those enrolled with ≥12 months termed “established.” We adjusted for age, sex, urban/rural status, and duration of ART dispensing.Of 88,556 patients enrolled in a DSD model, 4% (n=3,143) and 8% (n=6,714) had initiated ART <6 months or 6-12 months before DSD entry, respectively. Early enrollers were less likely to be LTFU at 12 months than established patients (adjusted risk ratio (aRR) [95% confidence interval] for <6 months on ART 0.72 [0.62-0.83]; aRR 0.74 [0.67-0.82] for 6-12 months on ART) for almost all DSD models and dispensing durations. A limitation of the analysis is that early enrollers may have been selected for DSD participation due to providers’ expectations about future retention.Patients enrolled in DSD models in Zambia after less than a year on ART were more likely to be retained in care 12 months later than were patients established on ART at DSD enrollment. Offering enrollment to at least some newly-initiating ART patients may improve ART programme outcomes.