New System Improves Distribution of Donated Livers
TUESDAY, Nov. 25 -- Thanks to a new liver transplant allocation system that gives preference to patients with the greatest need, rather than time spent on a waiting list, racial disparities among those waiting for new livers are narrowing.
Blacks are no longer much more likely to die or become too sick for a transplant while on the waiting list, although there are still noticeable gender gaps, according to the study published in the Nov. 26 issue of the Journal of the American Medical Association.
The new MELD (Model for End-Stage Liver Disease) scoring system was introduced in 2002.
"Post-MELD, the disparity between blacks and whites went away," said Dr. Cynthia A. Moylan, lead author of the study and a transplant hepatology fellow at Duke University Medical Center in Durham, N.C. "The sickest patients get" the organs, she said.
The study is the first comprehensive look at the success of the new system.
Currently, there are more than 16,000 people in the United States waiting for a new liver, according to the United Network for Organ Sharing (UNOS). And according to an accompanying editorial in the journal, overall survival rates for liver transplantations normally exceed 90 percent one year after the surgery. A liver transplant is the only hope for long-term survival for people with end-stage liver disease.
Prior to 2002, allocation of livers from deceased donors was based on time spent on the waiting list, as well as subjective measures by a physician, Moylan said.
"The system had multiple problems, and one was racial disparity," she said. 'They [blacks] were underrepresented on the waiting list and less likely to receive a transplant."
People who were able to wait for long periods of time were less likely to need a transplant, explained Dr. Richard Freeman, professor of surgery at Tufts University School of Medicine, in Boston, and chairman of the committee that put the MELD system into place.
Also, the old system could be manipulated. For instance, patients in intensive care were given preferential status, so doctors sometimes put patients in the ICU to bump them up on the list. "Doctors were trying to do the best thing for their patient, but it was disadvantaging those who really did need a transplant," Freeman said.
The MELD score, which predicts the risk of dying within three months, is based on a formula incorporating three laboratory tests.
"MELD is based on pure blood tests, and it's hard to manipulate patients' blood tests," Freeman said. "The waiting time is taken out. It's based on who's sicker."
The authors of the new study looked at patients, black and white, on the Organ Procurement and Transplantation Network waiting list for liver transplantation between Jan. 1, 1996, and Dec. 31, 2000 (pre-MELD), and between Feb. 28, 2002, and March 31, 2006 (post-MELD).
Before MELD, 27 percent of black patients died or became too sick for a transplant within three years of registering for a liver, compared with 21.7 percent of whites. After MELD, that gap narrowed considerably with 26 percent of blacks dying or becoming too sick for a transplant, compared with 22 percent of whites.
And while blacks were less likely than whites to receive a new liver within three years of registering on the pre-MELD list, in the post-MELD era this is no longer the case.
Gender, however, is another story. Women are more likely to die or become too sick for a liver transplant under the post-MELD system. And they are -- and were -- less likely to receive a new liver within three years, regardless of the era.
This likely is the result of several factors, including women's smaller size (meaning they need a smaller liver), higher likelihood of having an autoimmune disease, and the fact that women have less muscle mass, likely affecting some of the MELD calculations.
"Organ allocation in general is evolving all the time," Freeman said. "You learn how to do it better and build on your experiences to figure out what's wrong and what's right about it."
More evidence is emerging that adding a serum sodium test to the MELD calculation might right the gender imbalance.
Visit the United Network for Organ Sharing for more on organ donations and transplantation.
Posted: November 2008