Background: Scaling evidence-based interventions are key to impacting population health. The National DPP lifestyle change program is one such intervention that has been scaled across the USA over the past 20 years; however, enrollment is an ongoing challenge. Furthermore, little is known about which organizations are most successful with program delivery, enrollment, and scaling. This study aims to understand more about the internal and external organization factors that impact program implementation and reach.

Methods: Between August 2020 and January 2021, data were collected through semi-structured key informant interviews with 30 National DPP delivery organization implementers. This study uses a qualitative cross-case construct rating methodology to assess which Consolidated Framework for Implementation Research (CFIR) inner and outer setting constructs contributed (both in valence and magnitude) to the organization's current level of implementation reach (measured by average participant enrollment per year). A construct by case matrix was created with ratings for each CFIR construct by interviewee and grouped by implementation reach level.

Results: Across the 16 inner and outer setting constructs and subconstructs, the interviewees with greater enrollment per year provided stronger and more positive examples related to implementation and enrollment of the program, while the lower reach groups reported stronger and more negative examples across rated constructs. Four inner setting constructs/subconstructs (structural characteristics, compatibility, goals and feedback, and leadership engagement) were identified as "distinguishing" between enrollment reach levels based on the difference between groups by average rating, the examination of the number of extreme ratings within levels, and the thematic analysis of the content discussed. Within these constructs, factors such as organization size and administrative processes; program fit with existing organization services and programs; the presence of enrollment goals; and active leadership involvement in implementation were identified as influencing program reach.

Conclusions: Our study identified a number of influential CFIR constructs and their impact on National DPP implementation reach. These findings can be leveraged to improve efforts in recruiting and assisting delivery organizations to increase the reach and scale of the National DPP as well as other evidence-based interventions.