Impact of Cold Ischemia Time on Allograft Survival and Policy

Changes in national allocation policy and regulatory practices have led to increases in cold ischemia time (CIT) and out-of-sequence allocation (AOOS) or expedited placement (EP) of deceased donor kidney transplants in the United States. The aims of this study were to gauge the clinical relevance of the increased CIT that accompanied kidney allocation system (KAS) 250 NM (KAS250), and to measure CIT for AOOS or EP kidneys.

The United Network for Organ Sharing (UNOS) data from 2007 to 2023 were analyzed across pre-KAS, KAS, and KAS250 eras. The impact of CIT on kidney graft survival and the CIT of kidneys undergoing AOOS or EP during these eras was assessed.

Median CIT increased from 16 hours to 19.6 hours, and the incidence of AOOS or EP increased from 0.5% to 13%. Transplants with CIT of 32 to 36 hours had a 10% increase in overall graft loss compared with CIT of 16 to 20 hours (P = 0.0002). For kidney donor profile index (KDPI) 20% to 34% and 35% to 85% groups, every additional hour of CIT increased the risk of graft failure by 0.5% (P = 0.0019) and 0.4% (P < 0.0001), respectively. In the KAS250 era, CIT was 4 hours longer for AOOS or EP kidneys (P < 0.0001). In addition, AOOS or EP kidneys with KDPI > 85% declined from 9% to 7%, whereas AOOS or EP kidneys with KDPI < 20% increased from 13% to 15% (P = 0.0306).

Current allocation practices do not prioritize CIT. Extended CIT is associated with inferior long-term graft survival. AOOS or EP is designed to prevent discards but does not currently target high KDPI kidneys. Our data provide a framework to assess the relative importance of CIT in allocation policy.