Nov. 25, 2008 Following introduction of a new system in 2002 to determine the allocation of donated livers, black patients no longer are less likely to receive a liver transplant, but disparities for women remain, according to a new study.
The Model for End-Stage Liver Disease (MELD) score has been used by the Organ Procurement and Transplantation Network (OPTN) since February 2002 as the basis for allocation of deceased donor livers for transplantation among adults in the United States. The MELD score predicts the risk of death within 3 months and is based on objective laboratory variables: bilirubin (pigment in the bile that forms as a product of hemoglobin), creatinine (an end-product of protein metabolism found in the blood and urine), and a ratio for the prothrombin time (a clotting test). "In the current system, patients with higher MELD scores receive greater priority for organ allocation regardless of the amount of time spent on the waiting list," the authors write.
Cynthia A. Moylan, M.D., of Duke University Medical Center, Durham, N.C., and colleagues used a national database to determine whether racial or sex-based disparities exist in access to liver transplantation since the MELD system has been implemented. The study included adult black and white patients registered on the United Network for Organ Sharing liver transplantation waiting list between January 1996 and December 2000 (pre-MELD group, n = 21,895) and between February 2002 and March 2006 (post-MELD group, n = 23,793). Black patients, compared with white patients, were younger (average, 49.2 vs. 52.4 years) and sicker (MELD score at listing: median [midpoint], 16 vs. 14).
Analysis indicated that the odds of death or becoming too sick for liver transplantation within 3 years of listing were higher in black vs. white patients in the pre-MELD cohort (27.0 percent vs. 21.7 percent), but not in the post-MELD group (26.5 percent vs. 22.0 percent). The researchers also found that black patients were less likely than white patients to receive liver transplantation within 3 years of listing in the pre-MELD cohort but not in the post-MELD cohort.
"This elimination in racial disparity in the post-MELD cohort likely reflects the fact that the MELD score now accounts for the severity of a patient's disease when listed," the authors write.
Sex was significantly associated with death and liver transplantation after adjusting for race despite the use of the MELD score. Women were more likely to die or become too sick for liver transplantation within 3 years of listing in the post-MELD group (23.7 percent of women vs. 21.4 percent of men) but not in the pre-MELD group (22.4 percent of women vs. 21.9 percent of men). Women were also less likely to receive a liver transplant within 3 years of listing in both the pre-MELD and post-MELD groups.
"Sex differences persist despite the use of MELD. Whether these differences result from true anatomic differences or represent a problem not addressed by the use of the MELD score mandates further investigation," they write.
"The use of the MELD score allocation system appears to have reduced at least racial disparity in liver transplantation. We hope that ongoing investigations and refinements of MELD can provide even greater equity in the allocation of this precious resource."
The MELD system has helped decrease disparities regarding the allocation of donated livers, writes David A. Axelrod, M.D., M.B.A., of Dartmouth-Hitchcock Medical Center, Lebanon, N.H., and Elizabeth A. Pomfret, M.D., Ph.D., of Lahey Clinic Medical Center, Burlington, Mass., in an accompanying editorial.
"When compared with the system before 2002, the current MELD system is clearly a step toward achieving the goal of an equitable, efficient, and transparent organ allocation system. The MELD system appears to have reduced, but likely not eliminated, differential access based on race and ethnicity. However, modest differences based on sex persist, but could be addressed by revisions in the organ allocation policy to ensure that MELD scores are comparable across sexes."
"The sex disparity is likely a reflection of several factors, including a limitation in the MELD calculation, body and organ size considerations, and potentially differences in the etiology of the underlying liver disease."
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- Cynthia A. Moylan; Carla W. Brady; Jeffrey L. Johnson; Alastair D. Smith; Janet E. Tuttle-Newhall; Andrew J. Muir. Disparities in Liver Transplantation Before and After Introduction of the MELD Score. JAMA, 2008;300(20):2371-2378 [link]
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