The March 2021 implementation of the new kidney allocation system (KAS250) permits transport of deceased donor organs to transplant centers within 250 nautical miles. Investigators report that in the first 9 months since implementation deceased donor kidney transplantation increased among highly sensitized patients and those with longer dialysis vintage. The tradeoffs were that cold ischemia times and kidney discard rates increased.

Investigators compared kidney transplant outcomes during the first 9 months of KAS250 (March to December 2021) with a 2 year-period before KAS250 (March 2019 to March 14, 2021). Kidneys imported from non-local organ procurement organizations significantly increased from 27% before KAS250 to 59% afterward.

In keeping with the goals of KAS250, a significantly greater proportion of recipients with calculated panel reactive antibody 81%-98% received kidney transplants after implementation (12% vs 8%), Chethan M. Puttarajappa. MD, MS, of the University of Pittsburgh in Pennsylvania, and colleagues reported in the Journal of the American Society of Nephrology. Kidney transplantation also significantly increased among patients receiving more than 5 years of pretransplant dialysis (35% vs 33%).

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Cold ischemia time (CIT) significantly increased by a mean 2 hours (19.9 vs 17.9 hours), however, including among kidneys procured locally, the investigators reported. The rate of delayed graft function did not change.

After KAS250 implementation, kidney discard rates gradually increased for unclear reasons. Donor kidney quality was not a factor.

“Centers should consider various strategies such as the use of virtual crossmatch and machine perfusion to counter the prolonged CIT and improve organ utilization,” Dr Puttarajappa’s team wrote. “The trend noted in kidney discards needs close monitoring and additional studies to identify contributing factors and to develop improved strategies.”

The investigators acknowledged that the COVID-19 pandemic could have influenced results. They also pointed out that these early post-KAS250 trends may change over time.

Disclosure: Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.


Puttarajappa C, Hariharan S, Zhang X, et al. Early impact of the circular model of kidney allocation in the United States. J Am Soc Nephrol. Published online October 27, 2022. doi:10.1681/ASN.2022040471