Specification and Causal Pathway Diagramming of Implementation Strategies to Support Development of Access-Enhancing Injectable HIV Treatment Programmes at Eight Diverse Health Clinics Across the United States.

INTRODUCTION: Long-acting injectable antiretroviral therapy (LAI ART) represents a transformative development in HIV care because it may mitigate longstanding barriers that contribute to gaps in health outcomes. Providing LAI ART to people not consistently on HIV treatment or lacking treatment options requires intentional programme planning to overcome implementation barriers, without which only well-resourced patients benefit, worsening health outcome gaps. The ALAI UP Project delivered clinic-level implementation strategies to support eight clinics across Ending the HIV Epidemic jurisdictions to implement injectable cabotegravir and rilpivirine (iCAB/RPV).

METHODS: We specified seven implementation strategies and assessed their impact on clinic achievement of three key programme outcomes: (a) access to information about iCAB/RPV for all patients regardless of clinical eligibility; (b) access to iCAB/RPV regardless of healthcare coverage; and (c) access to iCAB/RPV for those who can clinically benefit the most, including patients who are unable to achieve durable viral suppression on oral ART for reasons other than cabotegravir or rilpivirine resistance. Implementation strategies were delivered from March 2023 through February 2025, and results are reported at the end of year 2 of the 3-year project. We developed causal pathway diagrams (CPDs) for each strategy, identifying determinants, preconditions, moderators, mechanisms and outcomes.

RESULTS: ALAI UP strategies supported clinic progress towards all three outcomes: six clinics had partially or fully achieved access to information about iCAB/RPV for all patients, seven clinics had partially or fully achieved access to iCAB/RPV for patients regardless of healthcare coverage, and six clinics had provided access to iCAB/RPV for those who could benefit the most clinically. By developing CPDs for each strategy, we explicated how strategies operated across different clinical contexts. Through this process, we identified mechanisms of action that needed to be activated, moderators that impacted strategy strength and preconditions that needed to be in place for the strategy to function. These insights informed changes to strategies in the final year of the project.

CONCLUSION: This work demonstrates that applying implementation science tools to service delivery projects can enhance precision and reproducibility of strategies, identify intervention points for improving strategies when mechanisms are not activated, and clarify hypothesized causal pathways testable in future hybrid effectiveness-implementation trials.