Five Long Island hospitals scored an A in patient safety in a national ranking by a medical quality and patient safety group.

The Leapfrog Group, founded in 2000 by large employers to improve health care quality and safety, issued on Wednesday its second Hospital Safety Score of more than 2,600 hospitals nationwide. Reviewing data on 26 measures from national surveys ranging from 2009 to 2011, the nonprofit assigned each hospital a score of A to F on how well it prevented errors, infections, injuries and medication mix-ups.

The group gave an A to John T. Mather Memorial Hospital in Port Jefferson; Nassau University Medical Center in East Meadow; St. Catherine of Siena in Smithtown; St. Francis Hospital in Roslyn; and Stony Brook University Hospital.

Long Beach Medical Center, currently closed because of damage caused by superstorm Sandy, was the only Long Island hospital to score a D.

Ten Long Island hospitals scored a C; seven scored a B. Overall, New York's 157 hospitals ranked 33rd nationally.

Mather, St. Francis and Stony Brook had scored an A in Leapfrog's first hospital safety ranking issued last spring. St. Catherine had scored a B and NUMC a C.

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Maureen Shannon, NUMC's vice president of quality management, said the hospital's top score came from "rigorous adherence to evidence-based practice guidelines."

Mather president Kenneth Roberts attributed his hospital's second A to "a culture of safety."

To see the rankings, visit hospitalsafetyscore.org.