Longitudinal Care Cascade Outcomes among People Eligible for ART who are Newly Linking to Care in Zambia: A Multi-State Analysis.

BACKGROUND: Retention in HIV care is dynamic with patients frequently transitioning in and out of care. Analytical approaches (e.g., survival analyses) commonly used to assess HIV care cascade outcomes fail to capture such transitions and therefore incompletely represent care outcomes over time. METHODS: We analyzed ART-eligible adults newly linking to care at 64 clinics in Zambia between April 1, 2014 and July 31, 2015. We used electronic medical record data and supplemented this with updated care outcomes ascertained by tracing a multistage random sample of patients lost to follow-up (LTFU, >90 days late for last appointment). We performed multi-state analyses, incorporating weights from sampling, to estimate the prevalence of nine care states over time since linkage with respect to ART initiation, retention in care, transfers, and mortality. RESULTS: 23,227 patients (58% female; median age 34y [IQR 28-41]) were ART-eligible at enrollment. At one year, 75.2% had initiated ART and were in care: 61.8% were continuously retained, 6.1% had reengaged after LTFU, and 7.3% had transferred. 10.1% were LTFU within seven days of enrollment and 15.2% were LTFU at one year (6.7% prior to ART). One year after LTFU, 51.6% of those LTFU prior to ART remained out of care compared to 30.2% of those LTFU after initiating ART. Overall, 6.9% of patients had died by one year with 3.0% dying prior to ART. CONCLUSION: Multi-state analyses provide more complete assessments of longitudinal HIV cascade outcomes and reveal treatment gaps at distinct timepoints in care that will still need to be addressed even with universal treatment.