John T. Mather Memorial Hospital in Port Jefferson is the only hospital in the state to have earned an A eight times in a row and one of only 133 nationwide in a ranking on patient safety by a national health quality group.

Twice a year since spring 2012 -- eight times -- The Leapfrog Group has issued a report looking at 28 patient safety measures. The group, a nonprofit founded by large companies to improve health care quality and safety, grades hospitals from A to F on how well they prevented errors, injuries, infections and drug mix-ups. On Wednesday it issued its fall report on about 2,500 hospitals.

Seven Long Island hospitals, including the 248-bed Mather, scored an A and one a D in the latest report. That's up from five hospitals that scored A's six months earlier.

"Quality, safety and efficiency are primary to the culture here at Mather Hospital," Mather president Kenneth Roberts said.

For the fourth time in a row, Nassau University Medical Center in East Meadow and St. Charles Hospital in Port Jefferson, part of Catholic Health Services, scored A's. And for the second time in a row, Mercy Medical Center in Rockville Centre, also part of CHS, scored an A.

Huntington Hospital, South Nassau Communities Hospital in Oceanside and CHS's St. Catherine of Siena Medical Center in Smithtown also scored A's.

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Southside Hospital in Bay Shore scored a D. North Shore-LIJ Health System, of which Southside is a part, said in a statement that "whenever information contained in the various 'hospital report cards' identifies a potential quality issue, the public can be assured we are already aware of it and working aggressively to resolve it."

For the first time, St. Francis Hospital in Flower Hill did not earn an A, instead scoring a C. In a statement, the hospital, part of CHS, said the grade "does not accurately reflect the quality and level of care" and attributed the drop to "technical issues that prevented Leapfrog from considering important data from our electronic medical record system."

Overall, New York ranked 34th nationally in patient safety, up from 38th last spring.

Leapfrog uses measures from the Leapfrog Hospital Survey, the Agency for Healthcare Research and Quality, the Centers for Disease Control and Prevention, the Centers for Medicare & Medicaid Services and the American Hospital Association's Annual Survey and Health Information Technology Supplement.

For more information, go to hospitalsafetyscore.org.