Potential of Kidney Exchange Programs (KEPs) in Japan for Donor-Specific Antibody-Positive Kidney Transplants: A Questionnaire Survey on KEPs and a Multi-Institutional Study Conducting Virtual Cross-Matching Simulations.

Objectives: To clarify the need for a kidney exchange program (KEP) in Japan by conducting a questionnaire survey on KEPs and simulated KEPs by virtual cross-matching based on past cases of transplantation avoidance. Methods: In addition to the content regarding KEPs, an electronic survey was conducted to investigate the number of cases of kidney transplant abandonment due to "immunological" reasons over the past 10 years (2012-2021). Virtual cross-matching was conducted to simulate the feasibility of avoiding immunological risks and enabling kidney transplantation in patients who were previously unable to undergo the procedure. Results: The survey received responses from 107 facilities (response rate: 81.7%). In response to the question about the necessity of a KEP in Japan, 71 facilities (66.4%) indicated that KEPs are necessary. In addition, 251 living-donor kidney transplants were abandoned for "immunological" reasons over the past decade (2012-2021). Among the 80 pairs for which detailed information was available, virtual cross-matching simulations showed that 37/80 pairs (46.3%) were donor-specific antibody (DSA)-negative for blood type-matched combinations, and 41/80 pairs (51.3%) were DSA-negative for blood type-incompatible transplants. Conclusions: The need for a KEP in Japan and its potential usefulness were demonstrated.