By Bill Berkrot and Debra Sherman

ATLANTA (Reuters) - Use of genetic screening on heart patients helped cut hospitalizations related to the widely used blood thinner warfarin by nearly a third, according to a large study that marks a step forward in the fledgling field of personalized medicine.

Researchers found that patients who received a test of two genes connected to warfarin sensitivity were 31 percent less likely to be hospitalized for any cause during the first six months of the drug's use.

They were 28 percent less likely to be hospitalized for a bleeding episode or blood clot than those whose safe and effective warfarin dosing was determined by traditional trial and error method.

"What we find so wonderful about this is it's really harnessing the power of new science to reduce healthcare costs," Robert Epstein, chief medical officer for the study's sponsor, Medco Health Solutions Inc, said in an interview.

A subanalysis of the data found that if it excluded hospitalizations that occurred prior to genotyping, the argument for genetic screening was even stronger.

In that group, patients had a 43 percent lower risk of being hospitalized for bleeding or blood clot than those who did not receive the gene testing.

That result is likely to make insurance companies, and anyone looking to cut healthcare costs, sit up and take notice.

The genetic tests, which are easily done with a cheek swab or blood sample, need only be performed once ever for each patient and cost somewhere between $200 and $400 -- far less than even a brief hospital stay. However, the screening is not yet covered by most insurance companies.

"I think people have been looking for the kind of data that we generated," said Epstein, who presented the results at the American College of Cardiology scientific meeting in Atlanta.

"We're hoping that more folks will figure that this is a cost-effective alternative to the current way of dosing warfarin," he said. "If we reduce just two hospitalizations per 100 patients tested that more than compensates for the cost of genotyping."

Warfarin, the world's most widely prescribed blood thinner, is a highly effective drug to prevent blood clots and strokes that has been around since the 1940s. However, it is not without complications, requiring close patient monitoring to prevent serious bleeding or blood clots.

Because the effective dosing for a patient is very close to the dose that can cause harm, it must be tailored to the individual, typically using a trial and error method. That makes it a perfect candidate for personalized medicine -- a cause that Medco has championed.

"The test provides the information a physician needs to more precisely dose a patient so that an individual who has a low sensitivity to the drug can be dosed higher to minimize the risk of stroke and someone who is highly sensitive to the drug can be given a lower dose to avoid bleeding," said the Mayo Clinic's Thomas Moyer, co-lead investigator of the study.

Medco, which administers prescription drug benefits for employers and health plans, found in 2007 that about 1 million of the 60 million people on its rolls were taking warfarin, which is sold under the brand name Coumadin.

It also found that about 22 percent of them were being hospitalized within 6 months of starting the drug, Epstein recalled.

Medco decided to take a chance on the relatively new science and see if genotyping could make the difference.

Along with the Mayo Clinic, Medco conducted the study under which 896 patients were given the genetic screening early in their warfarin use, while 2,688 warfarin patients who did not get the gene test were also followed.

"This gives us more reassurance that the use of genetic testing can reduce costs as well as improve outcomes," Epstein said.

He said Medco's clients are increasingly embracing its efforts to advance personalized medicine.

"We have now got more than 200 clients paying us to genotype their members," a number Epstein said represents about 8 million people.

(Reporting by Bill Berkrot and Debra Sherman; Editing by Derek Caney, Dave Zimmerman)