Between fidelity and sustainability: a mixed-methods study of the implementation and healthcare utilization outcomes of two alcohol assertive outreach treatment models

Background: There is a gap between the model of Alcohol Assertive Outreach Treatment (AAOT) and its implementation. This study compared the implementation of AAOT in a high-fidelity service and a medium-fidelity service in the North West of England, with a focus on differences in healthcare utilization change and exploring stakeholder views on the fidelity and sustainability of each service’s adaptation of AAOT. Methods: A multistage mixed-methods design involving: 1) quantitative assessment and comparison of differences in healthcare utilization and treatment data pre- and post-AAOT implementation between services; and 2) qualitative exploration of the fidelity and sustainability of each service based on semi-structured interviews (n = 48), analyzed using the Framework Approach. Results: Both services showed reductions in Emergency Department visits and unplanned ward admissions (p <.001). Interviewees indicated that high-fidelity AAOT was more effective for service users with complex needs who previously struggled to engage with community specialist addiction treatment services, although sustainability challenges persist, reflecting barriers in commissioning processes and continuity of care. Conclusion: The AAOT model can be successfully adapted to different local contexts and reduce unplanned healthcare utilization despite sustainability challenges.