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UNOS contributes to study noting success in increasing minority kidney transplants through subtype matching

A study featured on the cover of the December 2015 edition of the American Journal of Transplantation documents the benefits of a systematic approach to match kidneys from deceased donors with subtypes of blood group A to blood type B recipients, most of whom are ethnic minorities. This has increased the rate of transplants for type B recipients, and they show no significant negative effects in short- to mid-term outcomes when compared to type B recipients transplanted with kidneys from type B donors. Since the end of the study period, this allocation process has been incorporated into national kidney allocation policy.

Type B is a relatively rare blood type and is not compatible with the blood types of many donors. As a result, type B candidates traditionally have been transplanted at a lower rate than candidates of any other blood group. Since Type B candidates are most commonly ethnic minorities, the disparity in transplant rates for people with this blood group may contribute to the overall lower transplant rates for minority patients. Type A is a common blood group in the donor population. Previous research and experience have shown that type A donors with two specific subtypes (A2 and A2B) are compatible with B candidates with low anti-A antibodies, thus providing these candidates additional transplant opportunities. Wida Cherikh, Ph.D., UNOS’ Assistant Director of Business Development and Senior Research Scientist, was a coauthor of the study, along with previous chairs of the OPTN/UNOS Minority Affairs Committee and a researcher from Midwest Transplant Network (the first organ procurement organization to pilot the A2/A2B to B allocation protocol). They studied the results of a committee-sponsored national variance established in 2002, where nine organ procurement organizations (OPOs) and their affiliated transplant centers chose to offer kidneys from subtype A2 and A2B deceased donors for compatible type B transplant candidates.

The researchers examined data from participating OPOs who recovered at least one kidney for transplantation from an A2 or A2B donor, as well as recipient data from transplant centers in the eight OPO service areas where A2 or A2B kidneys were transplanted into a B recipient between the years 2002 and 2011.

In this time, 101 candidates with blood type B received a kidney from an A2 or A2B donor. The proportion of transplants for type B recipients within the participating areas increased by 9.4 percent. Transplant rates decreased for recipients with blood type A and AB (7.4 percent and 5.5 percent, respectively), but the overall rates of transplants for these patients remained higher than their percentage of registrations on the waiting list. While 86 percent of the A2/A2B donors were Caucasian, 61 percent of the recipients with blood type B were ethnic minorities, suggesting the allocation protocol may help reduce disparity in transplant rates based on candidate ethnicity.

The researchers also compared post-transplant outcomes of type B recipients of A2/A2B kidneys to type B recipients of identical blood type B kidneys over the same time. They found no significant difference in key measures of short- or mid-term outcomes, such as graft survival (continued function of the transplanted kidney), patient survival, or early complications such as delayed graft function or organ rejection needing treatment when the recipient was initially discharged from the hospital.

In December 2014, as part of a set of changes to national kidney allocation policy, blood type B candidates who meet clinical criteria and give consent can be offered A2/A2B kidneys. While the overall enrollment of potentially eligible candidates has been low in the first several months of the new system, transplants of A2/A2B kidneys to type B recipients have occurred at a rate four times higher than the same time frame before adoption of the national policy.

To view the entire article, consult the following citation:

W.W. Williams, W.S. Cherikh, C. J. Young, P.Y. Fan, Y. Cheng, D. A. Distant, and C. F. Bryan. First Report on the OPTN National Variance: Allocation of A2/A2B Deceased Donor Kidneys to Blood Group B Increases Minority Transplantation. American Journal of Transplantation: Volume 15, No. 12, pages 3134-3142.

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