Transplant centers are more likely to accept marginal kidneys when placements are local and cold ischemia times are shorter, a new study finds.

Kidneys with prolonged cold ischemia times are associated with greater risk of graft failure and patient death, investigators led by Sanjay Mehrotra, PhD, of Northwestern University in Evanston, Illinois, noted in the Clinical Journal of the American Society of Nephrology. Previous research indicates rising risks with cold ischemia times longer than 12-24 hours.

Using 2018-2019 Organ Procurement and Transplantation Network data, the investigators modeled the probability of accepting an offer for a kidney after provisional acceptance. The model was based on logistic regression results for 3.33 million provisional acceptances from 12,369 donors and 108,313 candidates.

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For every 2 hours of cold ischemia time, the overall likelihood of kidney acceptance significantly decreased 25% and 12% for nonlocal and local recipients, respectively, the investigators reported.

“Transplant centers expectedly favor local offers (i.e. offers from donors within the same donor service area) over nonlocal offers with approximately every 2.5 hours of cold ischemia time for local recipients having the same impact on decision making for each accrued hour for nonlocal recipients,” Dr Mehrotra’s team wrote.

The model quantified the tradeoffs between cold ischemia time at the time of offer acceptance and donor-recipient characteristics. For high-risk kidneys (defined as a kidney donor risk index [KDRI] greater than1.75 or a kidney donor profile index [KDPI] greater than 85), every 2 hours of cold ischemia time significantly decreased the odds of kidney acceptance by 42% and 35% for nonlocal and local recipients, respectively. For kidneys with a KDRI of 1.75 or less, every 2 hours of cold ischemia time significantly decreased the odds of acceptance by 18% in nonlocal recipients, but did not influence local offers.

Transplant centers judged each hour of cold ischemia time more harshly for a high-KDRI kidney, according to the investigators. They estimated that a nonlocal offer with a reduced number of HLA-antigen mismatches had the same likelihood of full acceptance after a provisional acceptance as an offer with 70 minutes less cold ischemia time, all other criteria being equal.

The study findings have implications for the US kidney allocation system and may help reduce the kidney discard rate.

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.


Barah M, Kilambi V, Friedewald J, Mehrotra S. Implications of accumulated cold time for US kidney transplantation offer acceptance. Clin J Am Soc Nephrol. Published online July 22, 2022. doi:10.2215/CJN.01600222