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Patient Population Loss At A Large Pioneer Accountable Care Organization And Implications For Refining The Program.

  • Hsu, John1
  • Price, Mary2
  • Spirt, Jenna3
  • Vogeli, Christine4
  • Brand, Richard5
  • Chernew, Michael E6
  • Chaguturu, Sreekanth K7
  • Mohta, Namita8
  • Weil, Eric9
  • Ferris, Timothy10
  • 1 John Hsu ([email protected]) is director of the Clinical Economics and Policy Analysis Program, Mongan Institute, at Massachusetts General Hospital (MGH) and an associate professor in the Department of Medicine and in the Department of Health Care Policy at Harvard Medical School, both in Boston.
  • 2 Mary Price is an analyst in the Mongan Institute, MGH.
  • 3 Jenna Spirt is an analyst in the Mongan Institute, MGH.
  • 4 Christine Vogeli is an assistant professor in the Mongan Institute, MGH.
  • 5 Richard Brand is a professor emeritus of biostatistics at the University of California, San Francisco.
  • 6 Michael E. Chernew is a professor in the Department of Health Care Policy at Harvard Medical School.
  • 7 Sreekanth K. Chaguturu is vice president for Population Health at Partners HealthCare, in Boston; a staff physician at MGH; and an instructor in medicine at Harvard Medical School.
  • 8 Namita Mohta is a faculty member at the Center for Healthcare Delivery Sciences and a hospitalist at Brigham and Women's Hospital, in Boston.
  • 9 Eric Weil is the senior medical director for population health, Partners Healthcare; associate medical director of the Massachusetts General Physicians Organization, in Boston; and associate chief of clinical affairs, Division of General Internal Medicine, MGH.
  • 10 Timothy Ferris is the senior vice president, Population Health, at Partners Healthcare and MGH and an associate professor of Medicine at MGH and Harvard Medical School.
Published Article
Health affairs (Project Hope)
Publication Date
March 2016
DOI: 10.1377/hlthaff.2015.0805
PMID: 26953296


There is an ongoing move toward payment models that hold providers increasingly accountable for the care of their patients. The success of these new models depends in part on the stability of patient populations. We investigated the amount of population turnover in a large Medicare Pioneer accountable care organization (ACO) in the period 2012-14. We found that substantial numbers of beneficiaries became part of or left the ACO population during that period. For example, nearly one-third of beneficiaries who entered in 2012 left before 2014. Some of this turnover reflected that of ACO physicians-that is, beneficiaries whose physicians left the ACO were more likely to leave than those whose physicians remained. Some of the turnover also reflected changes in care delivery. For example, beneficiaries who were active in a care management program were less likely to leave the ACO than similar beneficiaries who had not yet started such a program. We recommend policy changes to increase the stability of ACO beneficiary populations, such as permitting lower cost sharing for care received within an ACO and requiring all beneficiaries to identify their primary care physician before being linked to an ACO.

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