8
Abstracts
6.1
IMPACT OF 1995 CHANGES IN THE UNOS ALLOCATION SYSTEM TL Lay. N Kyne, AA Zachary, and MS Leffell. Dept. of Medicine, Johns Hopkins University, Baltimore, MD We evaluated the impact of 1995 changes in the UNOS allocation system on waiting time, HLA mismatch, race, and PRA of renal transplant recipients. For nonmandatory share transplants, we observed: (1) a significant increase in the average waiting time of patients transplanted (539->808 days, P=0.01); (2) an increase, of borderline significance, in the proportion of transplants occurring in African-Americans (45 -->58%) ; (3) almost no change in the average number of mismatched HLA antigens (3.4 ->3.5); and (4) a small increase in the average PRA value (19->25%). We routinely perform final cross matches on the top 15 patients on the match list. We noted that, after the changes in the point system, the number of positive crossmatches among patients at the top of the list nearly doubled (P=0.02). There was a 70% increase in the proportion of mandatory share transplants. Although the frequency of these transplants was greater in Caucasians than in African-Americans, both before and after the change in the point system, a greater increase was experienced by African-Americans than by Caucasians. Of the mandatory share transplants, 76% were zero mismatches and 24% were phenotypically identical. During the study period, the size of the waiting list increased by nearly 60% and there was a significant (P<0.0001) increase in the proportion of patients waiting> 730 days; but there were no appreciable changes in the ABO or racial distribution. Among donors, the only notable change was an increase in the frequency of African-American donors in the later epoch. Increases in waiting time and frequency of mandatory shares were probably affected by both changes in the UNOS point system and in the size and composition of our waiting list. While the change in the mandatory share rule increased the frequency of good matches in AfricanAmericans, increasing the waiting time may have increased the frequency of positive crossmatches which could be reflected in the cost and time needed for testing.
6.1
A STUDY OF 3 YEARS OF KIDNEY ALLOCATION USING AMINO ACID RESIDUE MATCHING. S Takemoto, M Abe, JD McClelland, PI Terasaki, Tissue Typing Laboratory, University of California, Los Angeles, CA. In April, 1993, the kidney allocation protocol in Los Angeles was changed to promote transplantation of recipients with zero mismatches of HLA amino acid residues that were shown to correlate with serologically defined HLA cross reactive groups. Through April 1996, 129 of 696 kidneys were transplanted in recipients with O-residues mismatched. With the additional 89 kidneys transplanted to recipients with o A,B,DR mismatches, 31 % of kidneys were allocated to recipients with zero HLA or residue mismatches. The short term survival for these kidneys (84 +/- 4% at 1 year) was comparable to that of O-ABDR mismatched kidneys but not significantly different from mismatched kidneys. Longer follow-up is necessary to address long-term results. 20% of White, 18% of Black, 19% of Hispanic and 15% of other race recipients received kidneys with zero residues mismatched. Match runs and crossmatch results were examined for 102 locally procured donors in 1995. At least one O-residue mismatched recipient was identified for 35 of the donors and multiple recipients for 17 donors. Only 19% of the identified recipients received the kidney. The kidney was allocated to another recipient for 38% of cases; the patient was ill, unavailable or inactive for 8%; 15% were not transplanted because of administrative or donor quality issues; and 15% because of a positive crossmatch. Of the recipients with a positive crossmatch, 80% were awaiting a retransplant. Residue matching has provided equitable access to matched kidneys and has resulted in minimal positive crossmatches.