ACOs of diverse structures perform comparably on core MSSP quality and spending measures. CMS should maintain its flexibility and continue to support participation of diverse ACOs. Future research to identify modifiable organizational factors that account for performance variation within ACO types may provide insight as to how best to improve ACO performance based on organizational structure and ownership.

Purpose Although much research has been done on accountable care organizations (ACOs), little is known about their impact on rural hospitals. We examine the association between rural hospitals’ participation in an ACO and their performance on utilization and financial measures. Methods This quasi‐experimental study estimates the relationship between voluntary ACO participation and hospital metrics using propensity score‐matched, longitudinal regression models with year and hospital fixed effects. Regression models controlled for secular trends and time‐varying hospital and county characteristics. Hospital measures were from the American Hospital Association, RAND Hospital Data, and Leavitt Partners. The initial population comprises 643 rural hospitals that participated in an ACO for at least one year during the 2011 to 2018 study period and 1,541 rural hospitals that did not participate in an ACO. From this population we created a sample of propensity score‐matched hospitals consisting of 525 ACO‐participating and 525 comparable non‐ACO hospitals. Results Rural hospitals’ participation in an ACO is not associated with changes in hospital utilization or financial measures, nor is there an association between these performance metrics and whether another within‐county hospital participated in an ACO. A secondary analysis limited to Critical Access Hospitals provides some evidence that inpatient utilization increases in the second year of ACO participation, though the increases are not significant in year 3 and beyond. Conclusion We find no evidence that rural hospitals experience substantive changes in outpatient visits, inpatient utilization, or operating margin in the years immediately after joining an ACO.

Background: Multispecialty clinical settings are increasingly prevalent because of the growing complexity in health care, revealing challenges with overlaps in expertise. We study hospitalists and inpatient specialists to gain insights on how physicians with shared expertise may differentiate themselves in practice. Purpose: The aim of this study was to explore how hospitalists differentiate themselves from other inpatient physicians when treating patient cases in areas of shared expertise, focusing on differences in patient populations, practice patterns, and performance on cost and quality metrics. Methodology: We use mixed-effects multilevel models and mediation models to analyze medical records and disaggregated billing data for admissions to a large urban pediatric hospital from January 1, 2009, to August 31, 2015. Results: In areas of shared physician expertise, patients with more ambiguous diagnoses and multiple chronic conditions are more likely to be assigned to a hospitalist. Controlling for differences in patient populations, hospitalists order laboratory tests and medications at lower rates than specialists. Hospitalists' laboratory testing rate had a significant mediating role in their lower total charges and lower odds of their patients experiencing any nonsurgical adverse events compared to specialists, though hospitalists did not differ from specialists in 30-and 90day readmission rates. Practice Implications: Physicians with shared expertise, such as hospitalists and inpatient specialists, differentiate their roles through assignment to ambiguous diagnoses and multisystem conditions, and practice patterns such as laboratory and medication orders. Such differentiation can improve care coordination and establish professional identity when roles overlap.