Estimating the effect of increasing dispensing intervals on retention in care for people with HIV in Haiti

BACKGROUND: Multi-month dispensing (MMD) for antiretroviral therapy (ART) is a promising care strategy to improve HIV treatment adherence. The effectiveness of MMD in routine settings has not yet been evaluated within a causal inference framework. We analyzed data from a robust clinical data system to evaluate MMD in Haiti. METHODS: We assessed 1-year retention in care among 21,880 ART-naïve HIV-positive persons who started ART on or after January 1, 2017, up until November 1, 2018. We used an instrumental variable analysis to estimate the causal impact of MMD. This approach was used to address potential selection into specific dispensing intervals because MMD is not randomly applied to individuals. FINDINGS: We found that extending ART dispensing intervals increased the probability of retention at 12 months after ART initiation, with up to a 24·2%-point increase (95%CI: 21·9, 26·5) in the likelihood of retention with extending dispenses by 30 days for those receiving one-month dispenses. We observed statistically significant gains to retention with MMD with up to an approximately 4-month supply of ART; +5·1%-points (95%CI: 2·4,7·8). Increasing dispensing lengths for those already receiving ≥5-month supply of ART had a potentially negative effect on retention. INTERPRETATION: MMD for ART is an effective service delivery strategy that improves care retention for new ART recipients. There is a potentially negative effect of increasing prescription lengths for those new ART recipients already receiving longer ART supplies, though more research is needed to characterize this effect given medication supplies of this length are not common for newer ART recipients.