A national survey puts St. John’s Medical Center in the middle of the pack when it comes to hospital quality and safety.

But St. John’s officials don’t think much of the rating system, which they said is based on old information.

St. John’s received a “C” in its second year being judged in the survey. The grades, based on rates of preventable medical errors, injuries and infections, were released Wednesday by the Leap Frog Group.

St. John’s ranked worse than the national average in six categories, including the number of patients unnessessarily taking antibiotics and the percentage of surgery patients not receiving appropriate treatment for the prevention of blood clots.

The hospital fared better than the norm in eight categories. Among them: St. John’s had fewer than the average number of cases of patients’ wounds reopening after surgeries, and of patients suffering collapsed lungs due to medical treatment. The hospital also administered the correct antibiotic before surgery in 99 percent of recorded cases, better than the national average.

St. John’s officials said the so-so grade is inaccurate because it uses data that is a year and half old.

The survey also isn’t suited for small rural hospitals, they said. As a result, St. John’s chose not to participate in optional portions of the survey, further clouding the accuracy of the grade.

“We didn’t participate this year mainly because it’s not geared to hospitals our size,” hospital Chief Executive Lou Hochheiser said.

This year’s rating is based on information pulled from data St. John’s was required to report to the Centers for Medicare and Medicaid Services from July 2009 to September 2011. The rating was based only on statistics from Medicare patients, Hochheiser said.

Twelve indicators were left blank because the hospital chose not to provide information requested for the survey.

Last year, when the hospital provided information for the entire survey, St. John’s received poor marks. The letter grading system is new this year.

Hochheiser said this year’s results are misleading because some of the assessment criteria still don’t apply to small hospitals.

As an example, Hochheiser said, St. John’s scored a five out of 100 in a category that judges whether a hospital has adequate physician staff in its intensive care unit.

To score high in that category, a hospital must have an intensivist — a critical-care medicine specialist — in the department. But that’s not realistic for small hospitals, Hochheiser said.

“Why do you get dinged if it’s not appropriate to have one?” he said.

Representatives of the Leap Frog Group, a national nonprofit that promotes hospital openness, could not be reached Wednesday.

But a spokeswoman for the group said in an email that many hospitals, includ-ing rural ones, were awarded “As” in the survey.

St. John’s would have scored better on the survey had up-to-date CMS information been used, Chief Nursing Officer Lynn Kirman said.

Thus far in 2012, 98 percent of St. John’s surgery patients have received timely, appropriate treatment to prevent blood clots, Kirman said.

The rate cited in the Leap Frog survey is 85 percent.

Other categories also are better this year, Kirman said.

Hochheiser said he would support participating in an improved survey.

“It’s got to be a better survey. It’s got to be more up to date,” he said. “It would be great if we had real-time data that could be published and people could compare.”

Cheyenne Regional Medical Center was the only hospital out of the eight noncritical-access Wyoming hospitals in the survey to receive an “A.” Three others earned a “B” grade. The rest were given “Cs” from Leap Frog.