Impact of Cold Ischemia Time and Donor Age on Donation After Circulatory Death Kidney Transplant Outcomes: A UNOS Mate-Kidney Analysis

Abstract

Background: The association between prolonged cold ischemia times (CIT), donor age, and outcomes in kidney transplant recipients (KTRs) from donors after circulatory death (DCD) remains uncertain. We aimed to compare allograft outcomes in DCD-donor KTRs according to CIT and age.

Methods: UNOS database study (2010-2024) of DCD-donor KTRs on tacrolimus maintenance. We developed a mate-kidney analysis, comparing outcomes where one mate kidney had CIT >24 and the other ≤24 h. We evaluated patient death, all-cause allograft failure, and death-censored graft failure (DCGF) using multivariable stratified Cox proportional hazards models. We compared outcomes across age groups (≥50 or <50 years) and 6-h-period CIT deltas between mate kidneys. We assessed delayed graft function (DGF) occurrence with multivariable conditional logistic regression.

Results: We included 4092 DCD-donor mate-kidney pairs. There were no differences between CIT >24 versus ≤24 h in patient death (aHR 1.12, 95% CI 0.97-1.30), all-cause allograft failure (aHR 1.10, 95% CI 0.98-1.24), or DCGF (aHR 1.07, 95% CI 0.90-1.27). Similar results were observed when comparing outcomes by age group and 6-h-period CIT deltas between mate kidneys. Compared to shorter CITs, CITs >24 h were associated with increased DGF likelihood (aOR 1.42, 95% CI 1.25-1.60), as were increasing CIT deltas.

Conclusion: CITs >24 h in DCD-donor KTRs were not associated with adverse allograft outcomes, irrespective of age group. However, prolonged CITs were associated with increased DGF likelihood. Increasing the acceptance of both mate kidney from DCD donors should be considered despite projected CITs >24 h.

Keywords: Cold Ischemia time; Donation after cardiac death; cohort studies; kidney transplantation; mate kidney analysis.