The risk of graft loss 5 years after kidney transplantation is increased if cold ischemia time exceeds 14 hours

Abstract

Background: The state of the evidence is unclear regarding the impact of cold ischemia time (CIT) on the outcome of kidney transplantation. The aim of this study was to investigate the effect of CIT on the short- and long-term function of kidneys transplanted at the Sahlgrenska University Hospital in 2007-2009 from donors after brain death (DBDs).

Methods: This study was designed as a retrospective analysis of data from local and national transplantation registers. The study endpoints were as follows: delayed graft function (DGF), primary nonfunction (PNF), biopsy-proven acute rejection (BPAR), serum creatinine (S-creatinine) level at discharge, days of hospitalization after transplantation, and graft survival at 5 years post-transplantation. Adjusted regression analyses were used to determine causal relationships with CIT. A further aim was to estimate a threshold for CIT by analyzing event rates and coordinates of the receiver-operated characteristic (ROC) curve.

Results: There was a causal relationship between CIT as a continuous variable and the following endpoints: graft survival at 5 years post-transplantation, though this was not significant (hazard ratio (HR) 1.07, P = 0.057), DGF (odds ratio (OR) 1.09, P = 0.03) and S-creatinine (P = 0.003). In our material, the risk for impaired outcome was higher with longer CIT. We were therefore able to estimate a threshold value for CIT, set to 14 hours for both graft survival at 5 years post-transplantation and DGF. This was proved with significance by analyzing both event rates and the coordinates of the ROC curve. The risk of graft loss increased, with HR 2.3 (P = 0.023), when comparing a CIT cutoff of ≥14 hours with CIT < 14 hours. Delayed graft function increased, with an OR of 2.6 (P = 0.001).

Conclusion: Our study confirms that, in this patient material, longer CIT was associated with increased risk for both impaired graft survival and incidence of DGF. We estimated a threshold for CIT of 14 hours.

Keywords: cold ischemia time; graft survival; kidney transplantation; long-term function; short-term function.