The Obama administration proposed much-anticipated rules Thursday to spur changes in the way that health care for older Americans is organized and paid for. Here are key details:

1 What does it mean? The rules lay out a path for doctors, hospitals and other providers of care to form teams called "accountable care organizations," which, supporters say, would save money by better coordinating medical services for Medicare patients. Under the rules, teams that treat patients for less money would be rewarded financially by the government if they also meet certain measures of quality.

2 What are ACOs? They are a form of managed care that differs from health maintenance organizations, which were widely unpopular. ACOs are run by doctors or hospitals, rather than by insurance companies. Some ACOs already have sprung up, but the federal law enacted a year ago to overhaul the nation's health care system tries to spur their development by weaving them into the large Medicare program. To qualify as an ACO, the rules say, the doctors or hospitals that run one must be able to provide primary care for at least 5,000 patients.

3 Who would be affected? The Obama administration hopes many of the more than 45 million seniors and others who rely on Medicare will ultimately get their care this way; the administration's early estimates are that 1.5 million to 4 million people would participate by 2014. But it remains unclear how many doctors will sign up to start ACO's next year.

4 How much would be saved? Health and Human Services officials predicted Thursday that the Medicare ACOs will save the financially strained program $510 million to $960 million during the first three years after they go into effect next January.

5 What do patients have to do? Unlike in Medicare Advantage, the managed-care part of Medicare, patients will not sign up for an accountable care organization. Instead, they will be assigned to one after the fact if their primary doctor belongs to it. The rules call for patients to be told whether their main doctors belong to an ACO.

6 What do critics say? Some doctors fear that the new approach will unfairly give the advantage to larger systems that can afford the computerized databases and other resources needed to coordinate care with hospitals and specialists. Critics have worried that the arrangements could become large health-care monopolies that could suppress competition for patients and, as a result, drive up costs.

7 What do supporters say? Donald Berwick, a Health and Human Services administrator, said ACOs would help unite what has been fragmented care for older patients who have several chronic medical problems, which sometimes are treated by doctors who do not communicate with one another. He said ACOs encourage doctors, hospitals, nurses and other care-givers to share medical records, emphasize preventive care and "invest in keeping people healthy."

8 How do the rules help new ACOs? Unlike well-developed ACOs, newer organizations will be shielded from any downside risk for the first two years.

9 How will quality be assessed? The 65 standards by which an ACO's quality will be judged fall into five areas. They are patients' experiences in getting care; the extent to which care is coordinated; patients' safety; the degree of emphasis on preventive health; and the effectiveness in treating patients who are sick and frail. Other rules are intended to prevent doctors or other care providers that band together from violating antitrust laws.

10 What's next? The HHS said it will hold open-door forums during a two-month public comment period. After that, officials will adjust the rules and issue them later this year. Learn more about the proposal at www.healthcare.gov.

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