BackgroundThe science of implementation has offered little toward understanding how different implementation strategies work. To improve outcomes of implementation efforts, the field needs precise, testable theories that describe the causal pathways through which implementation strategies function. In this perspective piece, we describe a four-step approach to developing causal pathway models for implementation strategies.Building causal modelsFirst, it is important to ensure that implementation strategies are appropriately specified. Some strategies in published compilations are well defined but may not be specified in terms of its core component that can have a reliable and measureable impact. Second, linkages between strategies and mechanisms need to be generated. Existing compilations do not offer mechanisms by which strategies act, or the processes or events through which an implementation strategy operates to affect desired implementation outcomes. Third, it is critical to identify proximal and distal outcomes the strategy is theorized to impact, with the former being direct, measurable products of the strategy and the latter being one of eight implementation outcomes (1). Finally, articulating effect modifiers, like preconditions and moderators, allow for an understanding of where, when, and why strategies have an effect on outcomes of interest.Future directionsWe argue for greater precision in use of terms for factors implicated in implementation processes; development of guidelines for selecting research design and study plans that account for practical constructs and allow for the study of mechanisms; psychometrically strong and pragmatic measures of mechanisms; and more robust curation of evidence for knowledge transfer and use.

Background: Understanding the mechanisms of implementation strategies (i.e., the processes by which strategies produce desired effects) is important for research to understand why a strategy did or did not achieve its intended effect, and it is important for practice to ensure strategies are designed and selected to directly target determinants or barriers. This study is a systematic review to characterize how mechanisms are conceptualized and measured, how they are studied and evaluated, and how much evidence exists for specific mechanisms. Methods: We systematically searched PubMed and CINAHL Plus for implementation studies published between January 1990 and August 2018 that included the terms "mechanism," "mediator," or "moderator." Two authors independently reviewed title and abstracts and then full texts for fit with our inclusion criteria of empirical studies of implementation in health care contexts. Authors extracted data regarding general study information, methods, results, and study design and mechanisms-specific information. Authors used the Mixed Methods Appraisal Tool to assess study quality. Results: Search strategies produced 2277 articles, of which 183 were included for full text review. From these we included for data extraction 39 articles plus an additional seven articles were hand-entered from only other review of implementation mechanisms (total = 46 included articles). Most included studies employed quantitative methods (73.9%), while 10.9% were qualitative and 15.2% were mixed methods. Nine unique versions of models testing mechanisms emerged. Fifty-three percent of the studies met half or fewer of the quality indicators. The majority of studies (84.8%) only met three or fewer of the seven criteria stipulated for establishing mechanisms. Conclusions: Researchers have undertaken a multitude of approaches to pursue mechanistic implementation research, but our review revealed substantive conceptual, methodological, and measurement issues that must be addressed in order to advance this critical research agenda. To move the field forward, there is need for greater precision to achieve conceptual clarity, attempts to generate testable hypotheses about how and why variables are related, and use of concrete behavioral indicators of proximal outcomes in the case of quantitative research and more directed inquiry in the case of qualitative research.

Background Public policy has tremendous impacts on population health. While policy development has been extensively studied, policy implementation research is newer and relies largely on qualitative methods. Quantitative measures are needed to disentangle differential impacts of policy implementation determinants (i.e., barriers and facilitators) and outcomes to ensure intended benefits are realized. Implementation outcomes include acceptability, adoption, appropriateness, compliance/fidelity, feasibility, penetration, sustainability, and costs. This systematic review identified quantitative measures that are used to assess health policy implementation determinants and outcomes and evaluated the quality of these measures. Methods Three frameworks guided the review: Implementation Outcomes Framework (Proctor et al.), Consolidated Framework for Implementation Research (Damschroder et al.), and Policy Implementation Determinants Framework (Bullock et al.). Six databases were searched: Medline, CINAHL Plus, PsycInfo, PAIS, ERIC, and Worldwide Political. Searches were limited to English language, peer-reviewed journal articles published January 1995 to April 2019. Search terms addressed four levels: health, public policy, implementation, and measurement. Empirical studies of public policies addressing physical or behavioral health with quantitative self-report or archival measures of policy implementation with at least two items assessing implementation outcomes or determinants were included. Consensus scoring of the Psychometric and Pragmatic Evidence Rating Scale assessed the quality of measures. Results Database searches yielded 8417 non-duplicate studies, with 870 (10.3%) undergoing full-text screening, yielding 66 studies. From the included studies, 70 unique measures were identified to quantitatively assess implementation outcomes and/or determinants. Acceptability, feasibility, appropriateness, and compliance were the most commonly measured implementation outcomes. Common determinants in the identified measures were organizational culture, implementation climate, and readiness for implementation, each aspects of the internal setting. Pragmatic quality ranged from adequate to good, with most measures freely available, brief, and at high school reading level. Few psychometric properties were reported. Conclusions Well-tested quantitative measures of implementation internal settings were under-utilized in policy studies. Further development and testing of external context measures are warranted. This review is intended to stimulate measure development and high-quality assessment of health policy implementation outcomes and determinants to help practitioners and researchers spread evidence-informed policies to improve population health. Registration Not registered