Last year a national group published safety scores for hospitals across the country. Now, there's a new tool for employers designed to help companies steer workers toward some hospitals and away from others.

When hospitals make mistakes and cause preventable injury and illness that then require more treatment, that's costly to patients—and the entire health care system. The Leapfrog Group says its new calculator uncovers the hidden surcharge for hospital errors.

David Knowlton, who used to work with Leapfrog and is now president of the nonprofit New Jersey Health Care Quality Institute, said the calculator could be a money-saver for budget-conscious managers.

Just think about all the expensive, time-consuming ways that employers try to lower health care costs, Knowlton said. Companies urge workers to get more exercise or join a lunchtime yoga class to relieve stress. When workers are at risk for obesity or diabetes, managers nudge them to join a case-management program or accept calls from a prevention nurse.

Knowlton said Leapfrog's new calculator sets apart hospitals that waste money on less-than-stellar care.

"Just by having somebody go to an 'A' hospital versus a 'D' hospital could save you almost $2,000 per patient," Knowlton said. "That's huge."

Three hospitals score low on Leapfrog scale

The calculator is based on Leapfrog's hospital rating system which drew praise and criticism last summer when it was released.

Leapfrog began as a business roundtable looking for ways to make sure employers get more value out of the money they invest in health care.

There are lots of hospital scorecards. Some consider consumer satisfaction or the number of board-certified doctors affiliated with a hospital. Knowlton said Leapfrog decided that avoiding medical errors and gauging safety is the most important way to rate a medical center.

In June 2012, Rich Umbdenstock, president of the American Hospital Association, wrote to Leapfrog expressing "disappointment that the scorecard's assessment was neither fair nor accurate."

Three hospitals in the Philadelphia region earned "D" grades from Leapfrog: Lower Bucks Hospital in Bristol, Pa.; South Jersey Healthcare—now called Inspira Health—in Vineland, N.J.; and Lourdes Medical Center of Burlington County in Willingboro, N.J.

Judgments based on single evaluation may not be enough

In an email, Lourdes Vice President of Corporate Development Kim Barnes said Leapfrog's methodology has several shortcomings.

"Their approach tends to over-emphasize the availability of systems, such as computerized physician order entry. CPOE is something that Lourdes has just recently implemented as part of a wide-ranging IT infrastructure initiative that we expect will positively impact our hospital safety score going forward," Barnes said.

Barnes urged people to consult several sources before picking a hospital.

Who's using the calculator?

Leapfrog's free calculator was released several days ago. It's not clear yet if the tool will motivate health care shoppers to choose another hospital or if companies will consult the tool as they make health plan decisions. But Knowlton said that's the goal.

"Every airline in America gets an 'A' in safety," Knowlton said. "They may have too-narrow seats. They may lose your luggage. They may take you to the wrong city. They may not leave on time. But if they get less than an 'A' on safety, they don't fly."

Knowlton said Leapfrog's vision for hospitals is the same: "If you don't get an 'A' in safety, you don't provide care."

Other ways to evaluate hospitals:

• Medicare's Hospital Compare

• The Joint Commission

• U.S. News and World Reports

• Healthgrades

• Consumer Reports