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An Accountable Care Organization (ACO) is a formal group of physicians, hospitals, or other care providers that voluntarily work together to deliver high-quality coordinated care to Medicare beneficiaries. The goal of an ACO is to provide affordable care through reducing or eliminating unnecessary duplication of tests or services, lowering the risk of medical errors. For each ACO, there is a defined patient population, primarily composed of Medicare beneficiaries, for which it is held accountable in terms of care cost, gross savings, and quality. 

The following list highlights the top 25 ACOs by patient population, representing over 15.7 million patients with an average population of 628,000.  Of the top 25, 92 percent are classified as commercial ACOs— an ACO model with a non-government payer.

TMA PracticeEdge, a commercial ACO based out of Austin, TX, ranks first with a patient population of five million — 112-percent higher than the next highest ACO, Aetna-Children’s Hospital of Philadelphia (CHOP) which has a patient population of 1.4 million. 

Top 25 Accountable Care Organizations by Patient Population 

Rank

Definitive ID

ACO Name

ACO Type

City

State

ACO Start Date

Patient Population

810909 

TMA PracticeEdge (Texas Medical Association - Blue Cross and Blue Shield of Texas ACO) 

Commercial ACO 

Austin 

TX 

2015 Q1 

5,000,000 

842940 

Aetna - Childrens Hospital of Philadelphia (CHOP) ACO 

Commercial ACO 

Philadelphia 

PA 

2015 Q4 

1,400,000 

552096 

Steward Integrated Care Network 

Medicare Next Generation ACO 

Needham 

MA 

2016 Q1 

1,000,000 

552289 

Aetna - Carilion Clinic ACO 

Commercial ACO 

Roanoke 

VA 

2011 Q3 

1,000,000 

552388 

Capital Bluecross - Heritage Medical Group ACO 

Commercial ACO 

Lemoyne 

PA 

2011 Q2 

700,000 

579844 

Anthem Blue Cross of California - Healthcare Partners ACO 

Commercial ACO 

Torrance 

CA 

2013 Q4 

675,000 

579912 

Aetna - Riverside Health System ACO 

Commercial ACO 

Newport News 

VA 

2013 Q2 

500,000 

585269 

Horizon Blue Cross Blue Shield of New Jersey - Partners in Care ACO 

Commercial ACO 

East Brunswick 

NJ 

2014 Q1 

500,000 

823406 

Aetna - Virtual Medical Group ACO 

Commercial ACO 

Marlton 

NJ 

2015 Q1 

400,000 

10 

552285 

Advocatecare ACO 

Commercial ACO 

Chicago 

IL 

2011 Q1 

375,000 

10 

969400 

BCBS Illinois - Advocate Physician Partners Accountable Care 

Commercial ACO 

Rolling Meadows 

IL 

2012 Q3 

375,000 

12 

969315 

BCBS Arizona - Banner Health Network ACO 

Commercial ACO 

Phoenix 

AZ 

2012 Q1 

350,000 

12 

553402 

Cigna - Banner Health Network ACO 

Commercial ACO 

Phoenix 

AZ 

2012 Q4 

350,000 

14 

577487 

UnitedHealthcare - Seton Health Alliance ACO 

Commercial ACO 

Austin 

TX 

2013 Q3 

320,000 

15 

578002 

Partners for Kids ACO 

Medicaid ACO 

Columbus 

OH 

2012 Q3 

300,000 

15 

969460 

HealthPartners - Northwest Metro Alliance 

Commercial ACO 

Bloomington 

MN 

2010 Q1  

300,000 

17 

585460 

Blue Shield of California - EPIC ACO 

Commercial ACO 

Redlands 

CA 

2014 Q1 

273,000 

18 

835846 

University Hospitals - Anthem Blue Cross and Blue Shield ACO 

Commercial ACO 

Cleveland 

OH 

2015 Q3 

270,000 

19 

849729 

Humana - DeKalb PHO ACO 

Commercial ACO 

Decatur 

GA 

2016 Q1 

250,000 

19 

858080 

DeKalb Medical Physicians Group - UnitedHealthcare ACO 

Commercial ACO 

Decatur 

GA 

2016 Q3 

250,000 

19 

947978 

Cigna - DeKalb Physicians Health Organization 

Commercial ACO 

Decatur 

GA 

2015 Q4 

250,000 

22 

552351 

Cigna - Westmed Medical Group ACO 

Commercial ACO 

Purchase 

NY 

2012 Q2 

237,000 

23 

553396 

OptumCare - North American Medical Management California ACO 

Commercial ACO 

Ontario 

CA 

2012 Q4 

229,000 

24 

574791 

Rainbow Care Connection 

Commercial ACO 

Cleveland 

OH 

2012 Q3 

200,000 

24 

777076 

Health Choice Utah 

Medicaid ACO 

South Jordan 

UT 

2013 Q1 

200,000 

Fig 1.  Data from Definitive Healthcare from the Accountable Care Organizations Database. Data is from the Center for Medicare & Medicaid Services and Definitive Healthcare proprietary data. Most recent data available, accessed in April 2020.