Accountable Care Organizations in the United States: market and demographic factors associated with formation.

BACKGROUND: The Accountable Care Organization (ACO) model is rapidly being implemented by Medicare, private payers, and states, but little is known about the scope of ACO implementation. OBJECTIVE: To determine the number of accountable care organizations in the United States, where they are located, and characteristics associated with ACO formation. STUDY DESIGN, METHODS, AND DATA: Cross-sectional study of all ACOs in the United States as of August 2012. We identified ACOs from multiple sources; documented service locations (practices, clinics, hospitals); and linked service locations to local areas, defined as Dartmouth Atlas hospital service areas. We used multivariate analysis to assess what characteristics were associated with local ACO presence. We examined demographic characteristics (2010 American Community Survey) and health care system characteristics (2010 Medicare fee-for-service claims data). PRINCIPAL FINDINGS: We identified 227 ACOs located in 27 percent of local areas. Fifty-five percent of the US population resides in these areas. HSA-level characteristics associated with ACO presence include higher performance on quality, higher Medicare per capita spending, fewer primary care physician groups, greater managed care penetration, lower poverty rates, and urban location. CONCLUSIONS: Much of the US population resides in areas where ACOs have been established. ACO formation has taken place where it may be easier to meet quality and cost targets. Wider adoption of the ACO model may require tailoring to local context.

Insights from transformations under way at four Brookings-Dartmouth accountable care organization pilot sites.

This cross-site comparison of the early experience of four provider organizations participating in the Brookings-Dartmouth Accountable Care Organization Collaborative identifies factors that sites perceived as enablers of successful ACO formation and performance. The four pilots varied in size, with between 7,000 and 50,000 attributed patients and 90 to 2,700 participating physicians. The sites had varying degrees of experience with performance-based payments; however, all formed collaborative new relationships with payers and created shared savings agreements linked to performance on quality measures. Each organization devoted major efforts to physician engagement. Policy makers now need to consider how to support and provide incentives for the successful formation of multipayer ACOs, and how to align private-sector and CMS performance measures. Linking providers to learning networks where payers and providers can address common technical issues could help. These sites' transitions to the new payment model constitutes an ongoing journey that will require continual adaptation in the structure of contracts and organizational attributes.