Background: Home-Based Primary Care (HBPC) is a unique home care program that provides comprehensive, longitudinal primary care to Veterans with complex chronic disease with an interdisciplinary team of VA staff. HBPC enrollment is associated with reduced hospitalizations, reduced health care costs, and high patient satisfaction, and is a critical component of the Office of Geriatrics and Extended Care’s (GEC’s) strategy to shift long term services and supports into home and community-based services. Significance: GEC plans to expand HBPC by 75 sites by 2026, but there is substantial variation in individual HBPC site structures, populations served, care delivery patterns, and clinical outcomes. It is unknown whether this variation represents variable fidelity to the HBPC clinical model and an opportunity to improve efficiency vs. appropriate flexibility and adaptation to varying patient needs and local contexts. Given planned expansion, a detailed understanding of program variation is needed to understand which configurations of program features are successful in what contexts and why. Innovation & Impact: This proposal uses configurational analysis, an emerging mixed-methods approach, to identify configurations of HBPC program and contextual characteristics associated with longer patient home time, a novel patient-centered outcome measure. Patient home time is a novel measure that captures a universal goal in HBPC, the time a Veteran can live independently at home. Results of this study will inform HBPC expansion and will help existing engage in context-tailored quality improvement efforts. Specific Aims: Aim 1: Assess variation among HBPC sites in contextual and modifiable factors, patient characteristics, and care delivery patterns, and identify site and patient level correlates of clinical outcomes. Aim 2: Assess HBPC team member and Veteran perspectives on potential mechanisms of success in sites that are high and low performing in patient home time. Aim 3: Identify factors that distinguish HBPC sites with higher versus lower performance in patient home time. Methodology: Aim 1 is a quantitative study in which we will build descriptive profiles of all 440 HBPC sites using VA and Medicare data and perform regression analysis and cluster analyses to examine site and patient level correlates of clinical outcomes. In Aim 2 we will perform qualitative interviews of HBPC clinicians, staff, and Veterans, and observation of work practices in 10 HBPC sites with high performance and 10 with low performance in patient home time. Aim 3 will use configurational analysis, a cross case analysis method rooted in mathematical set theory, to identify features identified in Aims 1 and 2 that are necessary and/or sufficient for longer patient home time. Next Steps/Implementation: We will work with partners in GEC to use identified configurations of HBPC site features to inform HBPC expansion, and to facilitate the development of a complexity informed, adaptive ...