Work

Soft kidney allocation improves HLA matching and maintains allocation order

Year: 2025

Type: article

Abstract: Kidney allocation scores aim to balance transplant efficacy and equity but often deprioritize Human Leukocyte Antigen (HLA) matching, leading to reduced graft lifespan and a higher risk of donor-specific antibodies (DSA). This study introduces a “soft allocation” strategy to improve HLA match rates while minimally disrupting the allocation queue or equity. Donors include directed-living (D-LD), non-directed-living (ND-LD), and deceased (DD) types. In the “soft allocation” system, instead of automatically assigning the kidney to the first person in line, the kidney is offered to the best HLA match among the top patients on the waiting list. The predefined size of the top patient group (typically 5–20 patients) is referred to as K. This approach preserves blood type and age compatibility while protecting patients with rare HLA types. Analysis of 95,250 US DD transplants shows an increase in HLA-A&B&DR match scores from 1.45 to 1.77. In 42 recent DD cases and 230 ND-LD transplants in Israel, match scores improved from 2.33 to 2.54 and from 1.34 to 2.03, respectively. Similar enhancements are observed in related donor–recipient pairs using crossover transplants, achieving a three-fold match improvement without worsening any recipient’s match. For predefined allocation rules, soft allocation enables significant HLA matching improvement with minimal impact on allocation order, benefiting both unrelated and related transplants. Future work will extend this approach to include sensitized donations. Current kidney transplant decision systems focus on fairness and efficiency, and often give limited emphasis to genetic compatibility (HLA matching), which is an important factor in determining how successful a transplant is. Poor genetic matching can shorten the lifespan of the transplanted kidney. In this study, we tested a more flexible way of allocating kidneys. Instead of automatically giving each kidney to the first person on a transplant list, the system presented here looks at the top few people and selects the one with the best genetic match, while keeping waiting time fair. Using real transplant data from the US and Israel, we showed that this approach improved genetic matching without delaying waiting patients vs the current allocation rules. It could help kidneys last longer in recipients and improve outcomes for more patients in the future. Israeli et al. test a more flexible method of matching donor kidneys to those in need of transplant, aiming to maximize compatibility while also accounting for need. Their results show that this method can improve matching without causing transplant delay.

Source: Communications Medicine

DOI: 10.1038/s43856-025-01232-8