Using a scoring system to evaluate kidneys from older donors increases the chance they will remain healthy if transplanted, according to a team of Italian doctors.

The findings could expand the pool of transplantable kidneys by 25 to 30 percent, said Dr. Giuseppe Remuzzi of the Mario Negri Institute for Pharmacological Research in Bergamo.

In the United States alone, 80,000 people are on the waiting list for a transplant and are instead receiving dialysis, which is much more expensive.

The Remuzzi team, reporting in the New England Journal of Medicine, found that better-scoring kidneys lasted at least two years in 91 percent of the recipients, even if the donors were aged 60 and older.

That's the survival rate for kidneys from younger donors, he said.

The recipients received one kidney if tissue samples from each donated organ scored a 0 to 3 on a 12-point health scale. Pathologists examined blood vessels, connective tissue and other structures in the kidneys.

Zero was the healthiest score. When the kidneys each scored a 6 or less, both were transplanted into the same recipient. Less-healthy kidneys were discarded.

"The idea was, you have to look at what you are transplanting," Remuzzi said in a telephone interview.

The tissue sample took about 15 minutes to evaluate and was taken as the kidney was removed from the cadaver.

Without such an evaluation, an age difference of 10 years can make a big difference in the success rate of a transplant.

The United Network for Organ Sharing says the failure rate for a kidney from someone who is age 70 or older is 24 percent higher than it is for a kidney from someone age 60 to 69.

With the scoring system, the rates were the same whether the donor was in his 60s, or much older.

"With this approach, selection criteria might be extended to increase the number of available transplants without increasing the risk of premature graft failure among recipients of kidneys from older donors," the Remuzzi team wrote in a letter to the Journal.

Remuzzi said that at his institution older donors now account for nearly 45 percent of transplants.

In a second study in the journal, Dr. David Talbot and colleagues at Freeman Hospital in Newcastle upon Tyne in Britain found that using a machine to preserve kidneys from dead donors greatly helped them last and stay suitable for transplant.