Medicare’s new comprehensive measure of hospital readmissions shows that at least 20 percent of the hospitals in Illinois, Maryland, Massachusetts, New Jersey, New York and Rhode Island have higher rates of patients returning than the national average.

Colorado, Hawaii, Idaho, North Carolina, Oregon, South Carolina, Utah and Washington led the states with the highest proportion of hospitals with low readmission rates. In those states, between 13 and 16 percent of hospitals came in below the national average, which was 16 percent of Medicare patients, the data show.

Since 2008, Medicare has been tracking hospital readmission rates and publishing those for three common ailments. In December, the government expanded its disclosure by publishing hospital rates of Medicare patients of all diagnoses who returned within a month for unplanned reasons from July 2011 through June 2012. At 364 hospitals, or 8 percent, patients returned more frequently than did patients at the average hospitals. Some of these facilities are among the most revered in the country, such as the Cleveland Clinic and Duke University Hospital in Durham, N.C.

Patients at 315 hospitals, or 7 percent of those rated across the country, were readmitted at a lower rate than the national average. They included Baylor University Medical Center in Dallas, California Pacific Medical Center in San Francisco and Intermountain Medical Center in Murray, Utah. The rest of the nation’s hospitals were rated as average.

The KHN chart at the bottom of this story lists all hospitals that did either better or worse than average on this measure, known as hospital-wide all cause unplanned readmissions.

The all-cause readmission rates are particularly significant because the Medicare Payment Advisory Commission (MedPAC), which advises Congress, has encouraged lawmakers to use this measure when determining financial penalties for hospitals in the Hospital Readmission Reduction Program. Medicare is currently fining 2,225 hospitals for excess readmissions for heart failure, heart attack and pneumonia patients. (The full penalty list is in this KHN interactive chart, and Medicare publishes the underlying data here.)

The number of cases of each of these three conditions for many hospitals is quite small, making it hard for the government to make accurate assessments of their readmission rates. Half of hospitals have 70 heart attack patients or fewer over a three year period. Nine out of 10 hospitals would have at least 1,100 cases of any kind over three years, making calculations more accurate, MedPAC said.

The hospital industry and some independent researchers have expressed reservations about all the readmissions measures. They say they do not reflect that some hospitals end up saving lives by being more aggressive in readmitting patients at early signs of trouble. They also complain that hospitals with large proportions of low-income patients often have higher readmission rates because those patients often don’t have the money for follow-up care and are more likely to lack their own primary care physician. Finally, while Medicare does take the degree of patient sickness into account when judging hospitals, academic medical centers say that the government analysis isn’t refined enough to fully notice which patients are sicker than others with the same ailment.

Some cities had particularly large numbers of high readmission hospitals, the data show:

Chicago: 19 hospitals including Northwestern Memorial Hospital, Rush University Medical Center and the University of Chicago Medical Center.

Brooklyn: 11 hospitals including Brookdale Hospital and Medical Center, Kingsbrook Jewish Medical Center and New York Methodist Hospital.

Philadelphia: 10 hospitals including Einstein Medical Center, the Hospital of the University of Pennsylvania and Thomas Jefferson University Hospital.

Baltimore: Seven hospitals including The Johns Hopkins Hospital and Johns Hopkins Bayview Medical Center, MedStar Good Samaritan Hospital and the University of Maryland’s Medical Center and Midtown Medical Center.

Manhattan: Seven hospitals including Beth Israel Medical Center in Manhattan, Lenox Hill Hospital, New York-Presbyterian Hospital and NYU Langone Medical Center.

Boston: Five hospitals: Beth Israel Deaconess Medical Center, Boston Medical Center, Brigham and Women’s Hospital and the Brigham’s Faulkner Hospital, and Tufts Medical Center.

Los Angeles: Four hospitals: California Hospital Medical Center, Hollywood Presbyterian Medical Center, Olympia Medical Center and Ronald Reagan UCLA Medical Center.

Miami: Four hospitals: Jackson Memorial Hospital, Kendall Regional Medical Center, University of Miami Hospital and Westchester General Hospital.

Out of all cities, Oklahoma City had the most hospitals with lower than average readmissions rates, with four scoring better than average.