Redefining low-threshold buprenorphine access in an integrated mobile clinic program: Factors associated with treatment retention

Introduction: The Spot mobile clinic provides low-threshold buprenorphine integrated with clinical and social services in Baltimore City, MD. In 2021, The Spot modified practices to improve engagement including providing extended prescriptions, reducing frequency of toxicology testing, giving up to six months to stabilize on medication, offering maximum doses (up to 32 mg total) daily, and utilizing telemedicine. This study characterizes care retention by examining both the total time in care and the percentage of time with buprenorphine prescription coverage during these practice changes, and examines factors associated with retention. Methods: This retrospective cohort study includes patients (n = 341) who received a buprenorphine prescription who initiated care on The Spot mobile clinic from September 2021 to October 2022, with follow-up through October 2023. We utilized the Cox proportional hazards model and Kaplan-Meier survival analyses to assess differences in care retention by the factors of patient demographics and clinical characteristics. Additionally, we performed sensitivity analyses using Poisson regression to examine differences between patients with 80 % or greater time with active prescription coverage versus <80 % of time with active prescription coverage. Results: After practice setting changes, retention in care at 90 days was 60 %. Patients whose maximum daily buprenorphine dose was 28 to 32 mg were 80 % less likely to discontinue treatment over the study period than those prescribed ≤16 mg (adjusted hazard ratio of discontinuation: 0.2 [95 % CI: 0.1–0.3]). Engaging in wound care or hepatitis C treatment was associated with higher retention in care, and individuals experiencing homelessness remained engaged at rates comparable to stably housed patients. Conclusion: Practice changes aimed to improve access to patient-centered, low-threshold buprenorphine treatment may increase retention in care. Notably, higher doses of buprenorphine and integrated treatment with wound care and hepatitis C treatment were associated with increased retention. Due to gaps in patient care, retention metrics should incorporate total time in care as well as percentage of time with an active buprenorphine prescription.