Warm ischemic time as a critical risk factor of graft failure from donors after cardiac death: A single-center experience over three decades in the Kidney Donor Profile Index/Kidney Donor Risk Index era in Japan

Objectives: To evaluate the prognostic value of the warm ischemic time and the validity of the Kidney Donor Profile Index/Kidney Donor Risk Index for predicting the survival of donors after cardiac death grafts. Methods: We retrospectively assessed 315 kidneys retrieved from donors after cardiac death at Fujita Health University Hospital, Toyoake, Aichi, Japan. The Kidney Donor Profile Index/Kidney Donor Risk Index was calculated and the grafts were enrolled. Results: The median follow-up period was 11.9 years. The Kidney Donor Profile Index had a markedly asymmetric distribution (median 94%), and the Kidney Donor Risk Index had high index rates (0.79–2.94, median 1.70). The overall 5-, 10- and 15-year graft survival rates were 67.5%, 52.1% and 38.9%, respectively. The Kidney Donor Profile Index correlated with graft survival. The 5-, 10- and 15-year graft survival rates for the Kidney Donor Profile Index <1.2 were 87.7%, 73.5% and 59.2%; those for the Kidney Donor Risk Index >2.0 were 55.0%, 34.7% and 22.1%, respectively. A Cox multivariate analysis identified the Kidney Donor Risk Index (hazard ratio 2.06, 95% confidence interval 1.48–2.86, P < 0.0001) and warm ischemic time (hazard ratio 1.21, 95% confidence interval 1.09–1.34, P = 0.0010) as independent risk factors for graft loss. The addition of warm ischemic time >30 min had a significant effect, as measured by the C-index (0.708–0.731, P = 0.032), improving the net reclassification improvement score (0.256, P = 0.0039) and integrated discrimination improvement score (0.042, P = 0.0022). Conclusions: The Kidney Donor Profile Index/Kidney Donor Risk Index is a good prognostic tool for determining the outcomes of donors after cardiac death grafts. However, the warm ischemic time should also be included in the allocation system for donors after cardiac death grafts.