January 11, 2007 ??A national exchange program in the Netherlands found successful matches for 49% of 146 living kidney donor-recipient pairs who had incompatible blood types or positive crossmatches. These 30-month results from a program embarked on in 2004 are reported in the December 27, 2006 issue of Transplantation.

"The full-hearted cooperation between 7 university transplant centers, including their [human leukocyte antigen] HLA laboratories, has resulted in a high number of participants, which is absolutely necessary for such an excellent success rate," the study's lead author, Marry de Klerk, MD, from the Erasmus Medical Center, in Rotterdam, the Netherlands, told Medscape.

Willing but Mismatched Donors

The group writes that in the Netherlands, over the past 3 decades, the median wait time for a kidney transplant has increased from under 1 year to 4 to 5 years. The favorable outcome of living kidney donation and the development of laparoscopic donor nephrectomy have increased the attractiveness of this procedure. Yet some transplant candidates and potential living kidney donors have either incompatible ABO blood types or have antibodies (are sensitized) to donor HLAs, resulting in a positive crossmatch. Patients might have a high level of sensitization ??a high panel reactive antibody (PRA) ??due to transfusions, pregnancy, or previous transplants. A protocol of using either plasmapheresis or immunoabsorption to remove the antibodies, followed by immunoglobulin therapy, has been used for such patients.

A less expensive strategy is a paired donor kidney exchange program, where, for example, 2 incompatible donor-recipient pairs are matched so that the kidney from one pair is given to the transplant candidate in the second pair, and vice versa. In the Netherlands, all 7 kidney transplant centers embarked on such a program in 2004. This article examines the 30-month results.

From January 2004 until June 2006, 146 incompatible donor-recipient pairs participated in the living donor kidney exchange program. (No incompatible donor-recipient pairs chose not to participate, Dr. de Klerk said.) Recipients had a median age of 51 years (range, 15 ??73) and had been on a cadaveric kidney transplant wait list for a median of 13 months (range, 0 ??172 months); donors had a median age of 52 years (range, 26 ??77). Of the donor-recipient pairs, 69 transplant candidates (48 women and 21 men) had a positive crossmatch with their potential donors, and 77 transplant candidates (31 women and 46 men) had an ABO blood type that was incompatible with their potential donors. The largest donor group consisted of partners (86/146, 59%).

Every 3 months, the participants could be registered for a computer match; during the study period, 10 match procedures were performed (combinations of 2 donor-recipient pairs until 2005, and combinations of up to 3 donor-recipient pairs since then). Allocation criteria were blood type (first identical and then compatible), match probability (the recipient with the lowest chance of finding a donor, based on compatible ABO type and acceptable HLA antigens within the donor population, was ranked first), wait time, and donor age. The 7 transplant centers had a common protocol that prescribed that the donor travel to the recipient's center and the surgical procedures take place simultaneously.

High Success Rate

Matching based on ABO blood types and unacceptable HLAs identified 1019 possible matches for 122 donor-recipient pairs, with no potential solutions for 24 pairs. Selection on the basis of match probability resulted in 72 new match combinations. The success rate was significantly higher in the positive-crossmatch group than in the incompatible-ABO-blood-type group.

Successful Matches Among Incompatible Donor-Recipient Pairs