Improving the quality and performance of healthcare delivery systems represents one of the most significant challenges facing government and society in the U.S. and internationally. A promising strategy for improving healthcare quality is the systematic implementation of research findings and related practices known to generate better outcomes than prevailing practices. Unfortunately, barriers to successful implementation of effective practices are considerable and not fully understood; and reliable, effective strategies to facilitate implementation, particularly on a routine basis, are underutilized.

In 1998, the U.S. Department of Veterans Affairs' (VA) Quality Enhancement Research Initiative (QUERI) was established to improve the quality of VA healthcare through the use of research-derived best practices. During QUERI's initial development, new organizational structures, roles and procedures were established to facilitate active participation and collaboration among a large, multi-disciplinary group of VA researchers, managers and other key stakeholders. For their part, QUERI researchers employed concepts and approaches from what has become known as implementation science, also encompassed in the literature by terms such as knowledge utilization, knowledge translation, and knowledge transfer 12. They quickly discovered challenges both to implementation and the effective conduct of implementation research – challenges that continue to be encountered today. These included the need for new research designs, methods and instruments 3456;better reporting templates 67; and increasing recognition that implementation is often incredibly complex 7. Additionally, it was noted that "while there are several theoretical or conceptual models to pursue for guidance, there remain [ed] a need for the literature to document... [related] field-level successes and failures [p. 173, 7]."

Given the limited guidance available to implementation researchers in the Program's early years, QUERI researchers tried not only well-known interventions and models from various fields but also innovative approaches 891011. Consideration of such diverse sources enabled QUERI researchers to better understand and address methodological issues and barriers to adoption and sustainability. Resultant QUERI implementation projects, with their "field-level successes and failures" 7 related to the use of such approaches, have produced a myriad of insights and refinements as described in the QUERI Series.

This Overview article introduces the QUERI Program and its guiding frameworks. The Overview also summarizes QUERI's progress and promise. Finally, it introduces the QUERI Series, which presents and illustrates QUERI's implementation research frameworks, as well as a range of other conceptual and practical tools designed to address the challenges of implementation and related research. Overall, this content offers insights for other health systems and researchers seeking to effectively apply research to improve the care of patients.

QUERI was created within the context of an internationally recognized transformation of the VA's healthcare delivery system. This transformation had at its core a "quality improvement lens" 1213, and involved a major redesign of organizational structures and policies, including implementation of innovative information technology and a new performance management/accountability program 14. Within this overall transformation, QUERI was established inside the Health Services and Research Development (HSR&D) arm of the VA to "purposely link research activities (which generate scientific evidence) to clinical care in as close to real time as possible [p. I-14, 15]," in order to enhance the "rapid adoption of best clinical practices and improvement in patient outcomes [p. I-14, 15]."

Even prior to QUERI, the VA had recognized the value of research to improving patient care by supporting an intramural research program whose statutory mission was to enhance the health of veterans 14. By embedding investigators within a fully integrated delivery system with a stable patient population and robust electronic health records, VA had unparalleled opportunities to translate clinical questions into research studies and research findings into clinical actions. For instance, since 1946, VA has conducted multi-site clinical trials and has maintained a network of regional support centers that facilitate the evaluation of both standard and novel therapies 16. VA's ability to conduct clinical trials of practical significance to the population it serves was well recognized as a resource that could generate evidence "ripe" for implementation 17. In fact, the VA has served to generate a good deal of the clinical evidence currently considered "best practice," such as the routine use of aspirin for acute coronary artery syndromes 18.

Additional VA work, primarily in the field of health services research, laid further groundwork for implementation by using electronic administrative and clinical data to identify both variations in practice patterns across VA facilities and the considerable gap between ideal and actual clinical practice. VA work also had identified the reality that doing the right research and disseminating its findings was insufficient to transform health care 19. In response, QUERI was created to generate research-driven initiatives to directly and rapidly achieve quality improvements, including measurable progress in system performance and health-related outcomes. Although "research-driven," QUERI activity was in reality to occur within the context of collaboration and cooperation among researchers, policy makers, and local leaders within VA's decentralized, geographically-based clinical delivery networks.

QUERI has been described previously in detail 2021 and findings from various QUERI projects have been published 8222324. To date, however, the implementation science frameworks and methodological approaches developed and employed by QUERI have not been well documented.

The core QUERI approach was designed by key VA health system and research leaders exploring new strategies for achieving rapid VA quality improvements [personal communication, J Demakis]. The original design included the need to involve researchers more directly and systematically in promoting guideline-based practice and reducing the gaps between routine practice and the best available evidence. Through QUERI, VA leadership envisioned a proactive, interactive and multi-faceted implementation role for health services researchers in the context of close collaboration between research, quality improvement (QI) and clinical leadership.

Key elements of the QUERI Program evolved over time. These include a set of disease or problem-focused QUERI Centers, a core set of program-wide goals, and a complex 6-step framework, or "process," that guides each Center's activities. A QUERI Center is an organizational structure that provides dedicated infrastructure support, including a core team consisting of a research coordinator, clinical coordinator and implementation research coordinator. This core team shares operational responsibility to implement the QUERI process (described below). QUERI Centers may be housed within a single VA facility or organized "virtually" across several sites, but each is tasked with system-wide, rather than solely local responsibility. These duties include: 1) establishing a network of affiliated researchers, 2) making contacts with local and national clinical and policy leaders, and 3) directing the work of the Center strategically by focusing on system-wide priorities for improvement 2021.

Each QUERI Center focuses on a specific patient population or condition that has been identified by VA leadership as a high-risk/high-volume priority for the health care system. There are currently nine such Centers (Chronic Heart Failure, Diabetes, HIV/Hepatitis, Ischemic Heart Disease, Mental Health, Polytrauma/Blast-Related Injuries, Spinal Cord Injury, Stroke, and Substance Use Disorders) 25. Each QUERI Center is guided by a multidisciplinary Executive Committee comprised of experts and key stakeholders. This group helps their respective Center develop strategic plans to prioritize and initiate activities addressing their designated clinical condition. Overall, each QUERI Center aims to create the following:

Seven of the QUERI Centers have been in existence for several years, and two were established more recently. Each Center has a program of research encompassing QUERI Steps 1 through 5/6. Development of a full portfolio of implementation-related research for each QUERI Center has taken time, given the following:

▪ The need for the QUERI Program to develop an understanding of its mission and to develop effective practice-oriented research activities and approaches for QUERI researchers and other stakeholders.

▪ The need for many QUERI researchers to obtain grounding in the field of implementation science and related disciplines (e.g., organizational science and anthropology), as well as in unfamiliar methods (e.g., formative evaluation and qualitative methods).

▪ Funding, proposal review and ethics review (Institutional Review Board) timelines.

▪ The need to develop frameworks and other tools to guide the envisioned implementation activity and research.

To develop and implement a comprehensive strategic plan, each QUERI Center has established a rich set of collaborative relationships involving numerous national and regional (VA and non-VA) stakeholder groups. These include, for example, VA's Office of Quality and Performance (responsible for VA's extensive performance measurement and feedback system) and directors of VA's 21 regional healthcare networks, each within a defined geographical area of the US. These networks comprise VA's full spectrum of healthcare delivery facilities, including primary, tertiary, long-term, and other specialized care. An additional file illustrates partnerships for one QUERI Center (See Additional File 3 Key Stroke QUERI Collaborators Diagram). These relationships form the basis for partnering with key policy and clinical stakeholders, recognized as critical to making implementation a "system" rather than solely a "research" or "researcher" issue.

Although QUERI should still be considered a work in progress, much like the overall field of implementation science, the results of QUERI efforts to study and improve VA healthcare delivery practices are documented in a growing body of journal articles and reports 272829303132. In particular, QUERI-related publications and presentations reflect the steps of the QUERI process, as follows (see Table 1): pre-implementation intervention studies establishing best practices or measurement tools, per Steps M and C 3334353637383940; research and related activities relevant to QUERI Steps 1 to 3, e.g., regarding best and current practices 41424344454647; activity relevant to QUERI Step 4/5/6 projects, including implementation trials and studies employing non-experimental designs 8224849505152535455; and specific outcomes of overall QUERI efforts 19. In terms of the latter, for example, the following have been demonstrated: improvement in evidence-based alcohol screening; expansion of the number of methadone clinics within VA for veterans with opioid dependence; increase in the proportion of veterans with spinal cord injury receiving influenza and pneumococcal vaccinations; and a change in a prevailing performance measure to improve eye care in diabetics by focusing policy on the needs of veterans at high risk for blindness 2324505556. Finally, a large regional-level demonstration project, guided by the Mental Health QUERI Center, is accumulating knowledge and laying the groundwork and support for the national spread and sustainability of evidence-based collaborative care for depression. This effort has achieved an unprecedented level of researcher involvement and linkage to stakeholders within an implementation project and has already led to a nationally-supported program to enhance primary care/mental health collaboration across the VA healthcare system 4857.

The implementation approaches underlying QUERI successes are just beginning to be documented and disseminated, particularly in relation to specific Step 4 demonstration projects and general contributions to implementation science. Some of these build upon the work of others in the field of implementation science, while others reflect innovations developed by QUERI. For example, previously published articles present a refined view of formative evaluation within implementation 9; the interconnection between theories, models, strategies, other tools, and planning 10; and an exploration of the concept of facilitation within the PARIHS (Promoting Action on Research Implementation in Health Systems) framework 11. However, the general use of such approaches in QUERI has not, up to now, been illustrated, and other QUERI-related frameworks have yet to be explicated. Describing these tools and their integration within QUERI projects is relevant for the field of implementation science, other healthcare delivery systems, and researchers interested in replicating or exploring QUERI's improvement model and insights. The purpose of this QUERI Series for Implementation Science is to document and share this information in the context of its use within QUERI Centers' programmatic implementation research (Tables 1 and 2). Thus, the Series articles demonstrate how QUERI conceptualizes, designs, enables and conducts implementation research, and, consequently, how it develops new insights into implementation science.

The QUERI Series opens with this Overview, describing the QUERI program, its operational QUERI Centers, and its key, overarching Frameworks. These articles are followed by papers that primarily represent QUERI Centers' work and then a set of responsive commentaries. The former papers focus on a range of QUERI implementation research approaches, implementation study issues and needs, implementation barriers and enabling factors at both micro and macro levels, and illustrative cases demonstrating the use of various implementation tools including the core 6-step process. Cumulatively, this Series describes a broad array of implementation research challenges, as well as potential approaches explored by QUERI researchers to meet those challenges. The commentaries at the end of the Series provide reflections on the potential value of QUERI and its related approaches from the perspective of both VA (non-QUERI) leadership and non-VA stakeholders.

Development and use of QUERI's implementation science frameworks and methodological approaches have generated excitement and frustration, enjoyed successes and encountered barriers, and continuously enhanced progress in the understanding of implementation concepts and strategies. Insights gained to date regarding implementation science are now being incorporated into the next phases of QUERI Center programmatic research. The full potential and influence of QUERI should emerge over the next few years a) as all Centers continue to progress from early pilots and demonstration projects to large-scale regional trials and b) as the organizational template for national implementation under development by the Mental Health QUERI Center is evaluated and replicated by others.

VA and QUERI are not unique in their efforts to employ research-based approaches to accelerate routine implementation of evidence into practice within an integrated delivery system, although QUERI's simultaneous pursuit of improvement and implementation research goals may be unique. However, the richly detailed descriptions of this still-evolving effort and its frameworks, other tools, and enabling processes should have applicability to implementation researchers as well as health system leaders. With this Series, publications appearing elsewhere, and considerable work-in-progress, QUERI is pleased to share its evidence-based implementation experiences and evolving conceptual knowledge with colleagues also engaged on the journey to close the gaps in implementation knowledge and clinical practice.

Brian Mittman is Co-Editor-in-Chief of Implementation Science; Joe Francis is a member of the Editorial Board. All editorial decisions regarding this article and all subsequent articles in the QUERI Series were made independently by Martin Eccles, Co-Editor-in-Chief, and Ian Graham, a member of the Editorial Board serving as special co-editor of the Series. The articles in the QUERI Series describe implementation research conducted within the Health Services Research and Development (HSR&D) Service of the U.S. Department of Veterans Affairs. VA HSR&D provides in-kind support for the journal Implementation Science, including salary support for Brian Mittman and support for editorial and copy editing services. VA HSR&D staff played no role in editorial decisions for the QUERI Series manuscripts. The primary author (CBS) has worked as a QUERI consultant for several years.

CBS drafted the initial form and all revisions of this manuscript. BSM has read and drafted substantial refinements, and JF has provided input, feedback and refinements to the initial and final versions. All authors agreed to the final manuscript.