Across the nation, as many as 500 ACOs are organizing or already delivering clinical services to as many as 43 million Americans

There is no better way to track the progress of accountable care organizations (ACOs) than to monitor a list of the largest ACOs in the United States. Many pathologists and clinical laboratory managers already serve patients who are enrolled in ACOs.

Oliver Wyman, a consulting firm headquartered in New York City, is tracking the development of ACOs in different regions of the nation. It recently published the statistics on the number of ACOs and estimated ACO enrollment.

Now 259 Medicare ACOs

Oliver Wyman says that as of early 2013, there were 259 Medicare accountable care organizations. At that time, Oliver Wyman estimated that there are between 37 million and 43 million Americans who are receiving care through an ACO. This is approximately 23% of the U.S. population.

From a variety of sources, Dark Daily assembled its best guess for the 15 largest ACOs that are currently operating in the United States, as follows:

15 Largest Accountable Care Organizations

Rank and ACO Name Location in U.S. Yr Formed No. Enrollees Cum. Number Enrollees
1. Advocate Partners Downers Grove, lL 1995 553,000 553,000
2. Partners HealthCare Boston, MA 2011 550,000 1,103,000
3. Allina Health Minneapolis, MN 2010 331,388 1,434,388
4. UnityPoint Health West Des Moines, IA 2011 266,490 1,700,878
5. Banner Health Network Phoenix, AZ 2011 240,000 1,940,878
6. OSF HealthCare System Peoria, IL 2011 110,000 2,050,878
7. UW Health ACO Madison, WI 2012 109,000 2,159,878
8. Heritage California ACO Northridge, CA 2011 92,500 2,252,378
9. Physician Organization of Michigan ACO Ann Arbor, MI 2012 83,200 2,335,578
10. AHS ACO Morristown, NJ 2010 81,000 2,416,578
11. Triad HealthCare Network Greensboro, NC 2011 63,800 2,480,378
12. Baylor Quality Alliance Dallas, TX 2011 44,000 2,524,378
13. Plus (North Texas ACO) Fort Worth, TX 2012 41,000 2,565,378
14. NewHealth Collaborative Akron, OH 2010 40,000 2,605,378
15. Accountable Care Network of Texas Temple, TX 2013 37,500 2,642,878
Source: ACOs’ public communications officers, public sources.

As the statistics provided above demonstrate, these 15 ACOs have total enrollment of approximately 2.7 million people. Florida has no ACOs that make this list, and California only has one ACO that makes the list of the 15 largest ACOs.

One expert who believes that growth in both the number of ACOs and the number of enrolled patients is slowing is David Muhlestein, Ph.D., Director of Research at Leavitt Partners, a healthcare intelligence company. “We estimate that the number of ACOs has grown from a few dozen at the end of 2010 to nearly 500 as of the end of September 2013.

After significant growth through the end of January of this year, only 35 new ACOs have been announced.

Three Factors Contributing to Slower Pace of ACO Formation

Muhlestein believes that the slowdown in the formation of new ACOs can be attributed to three factors. The first factor is that, among those health systems that want to be pioneers in this arena, most have already launched their ACOs.

Leavitt Partners’ Director of Research, David Muhlestein, Ph.D., believes that the decline in the number of new ACOs announced during the latter half of 2013 can be explained by three factors. He also expects the experience of existing ACOs during 2013 will be closely watched. Widespread ACO success during 2013 will encourage slower-moving organizations to move forward on their own plans to form an ACO. (Photo copyright Leavitt Partners.)

Leavitt Partners’ Director of Research, David Muhlestein, Ph.D., believes that the decline in the number of new ACOs announced during the latter half of 2013 can be explained by three factors. He also expects the experience of existing ACOs during 2013 will be closely watched. Widespread ACO success during 2013 will encourage slower-moving organizations to move forward on their own plans to form an ACO. (Photo copyright Leavitt Partners.)

Muhlestein noted that the second factor involves certain healthcare organizations that “are not, yet, willing to make the transition to accountable care or accept risk… These organizations, which we refer to as ‘followers,’ are waiting for a proven model to follow. They are not opposed to accepting risk, but until they see a viable pathway to follow, they are content to wait patiently on the sidelines.”

Muhlestein sees the third factor as the slow embrace of ACOs by private payers. In his view, healthcare organizations already participating in Medicare ACOs would like to add to the enrollment of their ACOs. “Existing ACOs have reported that in some markets there may be only one or two payers that are currently willing to enter into risk-bearing contracts. While this doesn’t change the number of ACOs, this acts as a significant barrier for existing ACOs that want to expand their number of covered lives.”

What can pathologists and clinical laboratory executives expect to see in the next year or two? That depends, stated Muhlestein. “Going forward, this rate of [ACO] renewal will be a strong indicator of whether potential ACOs will become actual ACOs.

The next 6-12 months, in particular, will be very important as ACOs that have been operational for 1-2 years will have the opportunity to renew or cancel their contracts,” he stated.

“If the vast majority (>95%) of ACOs renew their contracts, expect the growth of ACOs to begin again in earnest as the follower organizations begin to choose successful models to emulate,” continued Muhlestein. ”If a high number of ACOs fail to renew their contracts, the recent slowdown of the increase in ACO lives is unlikely to be temporary and future growth will be weak, if it continues at all.”

Related Information:

The ACO Surprise

Accountable Care Organizations Now Serve 14% of Americans

Why Has ACO Growth Slowed?

Obamacare’s Accountable Care Approach Reaches 1 in 10 In U.S.

ACOs: The New Rx for Health Care Delivery?