Distribution of Visits for Chronic Conditions Between Primary Care and Specialist Providers in Medicare Shared Savings Accountable Care Organizations

By Evan, S. Cole, Cassandra Leighton, and Yuting Zhang
Medical Care, May 2018

Accountable care organizations (ACOs) are groups of health care providers who agree to be collectively accountable for the overall care and costs of a prespecified group of patients. Medicare ACOs were initiated in 2012 as part of the Affordable Care Act. Since then, over 10.5 million Medicare beneficiaries have been served by 562 ACOs participating in Medicare ACO initiatives. The largest Medicare ACO program is the Medicare Shared Savings Program (MSSP): as of January 2017, there are 480 MSSP ACOs serving 9 million assigned beneficiaries nationwide. In a shared savings arrangement, providers are encouraged to manage the health care needs of a defined patient population in the most cost-effective manner.

Medicare beneficiaries are attributed to a MSSP ACO based on where they receive the majority of their primary care5; primary care is thus seen as a central component of the Medicare ACO model. Primary care has 4 main features: first contact for access to the health system, comprehensive care for most health needs, long-term focused care with an ongoing relationship, and coordinated care when needed elsewhere. It has been well-established that health systems that emphasize access to primary care have better outcomes and generally reduced costs compared with systems with poor access to primary care. A greater focus on primary care may occur within an ACO given their financial incentives. Research on Medicare’s ACO initiatives have found that ACOs with a strong primary care orientation and workforce achieved greater savings and better care in the beginning of the program, as measured by readmissions, quality of diabetes care, and provision of preventive services.

Although these preliminary findings are notable, research on the role of primary care within ACOs and how these organizations are strategically changing their practices to optimally use primary care providers (PCPs) is still emerging. ACOs may shift visits for chronic disease management to PCPs, who can manage these conditions concurrently with other comorbidities in a more accessible and less expensive manner than specialists. Hollingsworth et al analyzed data from the 2007 National Ambulatory Medical Care Survey on primary care and specialty providers and found that specialists provide routine management of 9 chronic conditions—care which could be reallocated to comprehensive primary care.

In this paper, we focus on 8 chronic conditions: asthma, chronic kidney disease (CKD), chronic obstructive pulmonary disease, diabetes, depression, hyperlipidemia, hypertension, and rheumatoid arthritis/osteoarthritis. We chose these conditions because these chronic conditions can be managed routinely and effectively by comprehensive primary care, but in practice both PCPs and specialists frequently manage the associated care. Specifically, we examine variation in the distribution of visits for 8 chronic conditions between primary and specialty care among MSSP ACOs and the factors affecting the variation. In addition, we descriptively compare this distribution of ambulatory care utilization within MSSP ACOs and a representative sample of non–ACO-attributed Medicare beneficiaries.

From the Conclusions

In this study, we sought to understand how visits for certain chronic conditions were distributed between PCPs and specialists within MSSP ACOs and the factors that were related to primary care management of chronic conditions within ACOs. Although in aggregate we did not find large differences between ACO and non–ACO-attributed beneficiaries, we did find notable variation across ACOs. Organizationally, ACOs with a higher proportion of contracted physicians who were PCPs had higher proportions of chronic condition visits that were delivered by PCPs. This relationship was consistent for 7 of the chronic conditions we included, with the one exception being depression. In addition, ACOs with more white beneficiaries, with higher prevalence of ≥3 comorbidities, in areas with larger proportions of college-educated individuals, and with greater numbers of specialists had a smaller share of chronic condition visits delivered by PCPs.

Our findings provide an indication of how MSSP ACOs have organized care for chronic conditions early in the program. As stated above, ACOs are incentivized to provide appropriate care in the least expensive setting possible; however, it does not appear that early in implementation ACOs have, at least as a group, transitioned chronic care into primary care compared with care for non-ACO Medicare beneficiaries.

The degree to which PCPs manage chronic conditions is related to both patient population, chronic condition, and organizational factors. Many ACOs may underutilize PCPs in this role, and thus could actively shift care to less expensive primary care for potential savings to payers. Barriers to that shift could include low numbers of PCPs contracted in the ACO, and existing referral patterns and patient relationships with specialists.


The concept of the accountable care organization is that a group of health care providers, working together, could provide more efficient, integrated care for which they are accountable, thus improving quality while reducing health care costs. For many fairly routine chronic conditions this seems like an ideal model to expand the use of primary care since previous studies have shown that “ACOs with a strong primary care orientation and workforce achieved greater savings and better care.”

Although “ACOs are incentivized to provide appropriate care in the least expensive setting possible,” according to this study, “it does not appear that early in implementation ACOs have, at least as a group, transitioned chronic care into primary care compared with care for non-ACO Medicare beneficiaries.”

An interesting finding is that ACOs with a greater number of white, college educated beneficiaries “had a smaller share of chronic condition visits delivered by primary care physicians.” This suggests that ACOS may be aligning themselves to provide two tiered health care. That is ironic since some studies have suggested that more specialized services for the better off increase health care costs yet may produce outcomes that are no better and perhaps even worse, perhaps because specialized services are sometimes more fragmented and less integrated.

The fact that we continue to perpetuate our highly fragmented, dysfunctional health care financing system may play some role in our inability to achieve higher performance at lower costs while including everyone, as all other wealthy nations have done. The system that seems ideal for the United States is a well designed single payer national health program – an improved Medicare for all. Isn’t it time that we take a serious look at a model that would actually work?

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