Women are less likely than men in the United States to get a life-saving liver transplant, perhaps because of physical differences between the two sexes, according to a study published on Tuesday.

The report from Dr. Cynthia Moylan and colleagues at Duke University Medical Center in Durham, North Carolina, also found that blacks have gained a more equal footing with whites for liver transplants since 2002, when a new system was put in place emphasizing severity of disease rather than length of time on a waiting list.

That same screening system has not helped women, said the study, which was published in this week’s Journal of the American Medical Association. It looked at more than 45,000 patients who were waiting for liver transplants before and after the system was changed in 2002.

The research team found that women were less likely than men to receive a transplant within three years of being put on a wait list under both the old and new systems.

“Sex differences persist despite the (new system),” the authors said. “Whether these differences result from true anatomic differences or represent a problem not addressed by the use of the (system) mandates further investigation.”

In an editorial in the same issue commenting on the study, Drs. David Axelrod of Dartmouth-Hitchcock Medical Center in Lebanon, New Hampshire, and Elizabeth Pomfret of the Lahey Clinic Medical Center in Burlington, Massachusetts, said women may get fewer transplants because of size differences.

“Women are smaller, limiting the pool of available organs,” they said. When a smaller liver becomes available it often goes instead to a child waiting for a transplant.

“In addition a small organ can be used in a larger individual but the converse is not always possible,” they said.

Another factor may be that one of the liver function measurements used to determine extent of the disease may show up at less severe levels in women because of their lesser body mass, the editorialists said.

The study found the odds of death or becoming too sick for a transplant were higher for blacks than whites before the screening change was made but that difference disappeared under the new system.

The authors said that is likely because blacks - who have a higher incidence of liver problems to begin with - tend to have more advanced stages of the disease by the time they are put on a waiting list.

Because the new system is based on risk of death rather than time on the list, that has helped equalize things. But the authors said blacks still face health care barriers, such as insurance and access to specialists, which result in delays in getting care.

In 2005 there were 6,500 liver transplants performed in the United States.

CHICAGO (Reuters)