# Novel Allocation Strategies Can Boost Kidney Exchange Programs: A Monte Carlo Simulation

## TL;DR

New allocation strategies in kidney exchange programs can significantly increase transplant rates for difficult-to-match patients.

## Contribution

A novel allocation algorithm with ABO-incompatible and HLA-incompatible matching is shown to improve transplant rates in kidney exchange programs.

## Key findings

- The novel algorithm increased transplant rates for incompatible pairs from 44% to 53%.
- Including unspecified donors increased transplant rates for incompatible pairs up to 64%.
- Allowing compatible pairs to participate in KEP matched 58% of them with fewer HLA mismatches.

## Abstract

Kidney exchange programs (KEPs) enhance access to living donor kidney transplantation. Nonetheless, transplant rates in KEP remain low for highly immunized and blood type O patients. In the Netherlands, a novel allocation algorithm is being implemented, allowing ABO-incompatible matching for long waiting patients, next to prioritization and ‘low-level’ HLA-incompatible matching for selected highly immunized patients. We simulated this novel algorithm along with additional scenarios, by using a retrospective, 6-year cohort of Dutch KEP. For each scenario, 30 simulations were repeated with Monte Carlo technique. The novel algorithm increased median KEP transplant rate for incompatible pairs (53% versus 44%, p < 0.001) and for difficult-to-match subgroups. HLA-incompatible matching increased transplant rate for selected highly immunized patients significantly, while participation with multiple donors per recipient did not. In additional simulations, including all non-KEP unspecified donors (n = 150) for local KEP participation increased transplant rate for incompatible pairs up to 64% (p < 0.001). Simulating additional KEP participation by compatible pairs (n = 149), on the condition a KEP match should have fewer HLA mismatches, resulted in 58% being matched in KEP. In conclusion, differential matching algorithms can boost KEP transplant rates, allowing incompatible matching for difficult-to-match subgroups, facilitating participation of unspecified donors, and optimizing the HLA matching of compatible pairs.

Infographic of a Monte Carlo simulation to novel algorithms for kidney exchange programs. It presents analyses of different scenarios like priority for difficult-to-match patients, incompatible matching, unspecified donor participation and kidney exchange participation by compatible pairs. The simulation was performed with data from the Dutch KEP (2018-2023). Key findings highlight improved transplantation rates for difficult-to-match and long waiting patients. One scenario with extra compatible pair participation showed that 58% of compatible pairs could find a better match via KEP, while simultaneously enabling 57 more transplants for incompatible pairs with statistical significance (p<0.001). Logos for ESOT and Transplant International are included.