Reducing discard is important for the US transplantation system because nearly 20% of the deceased donor kidneys are discarded. One cause for the discards is the avoidance of protracted cold ischemia times. Extended cold ischemia times at transplant are associated with additional risk of graft failure and patient mortality. A preference for local (within the same donor service area) or low–Kidney Donor Risk Index organs, the endogeneity of cold ischemia time during organ allocation, and the use of provisional offers all complicate the analysis of cold ischemia times’ influence on kidney acceptance decision making.

Using January 2018 to June 2019 Organ Procurement and Transplantation Network data, we modeled the probability of accepting an offer for a kidney after provisional acceptance. We use logistic regression that includes cold ischemia time, Kidney Donor Risk Index, and other covariates selected from literature. Endogeneity of cold ischemia time was treated by a two-stage instrumental variables approach.

Logistic regression results for 3.33 million provisional acceptances from 12,369 donors and 108,313 candidates quantify trade-offs between cold ischemia time at the time of offer acceptance and donor-recipient characteristics. Overall, each additional 2 hours of cold ischemia time affected acceptance for nonlocal and local recipients (odds ratio, 0.75; 95% confidence interval, 0.73 to 0.77, odds ratio, 0.88; 95% confidence interval, 0.86 to 0.91; P<0.001). For Kidney Donor Risk Index >1.75 (Kidney Donor Profile Index >85) kidneys, an additional 2 hours of cold ischemia time for nonlocal and local recipients was associated with acceptance with odds ratio, 0.58; 95% confidence interval, 0.54 to 0.63 (nonlocal) and odds ratio, 0.65; 95% confidence interval, 0.6 to 0.7 (local); P<0.001. The effect of an additional 2 hours of cold ischemia time on acceptance of kidneys with Kidney Donor Risk Index ≤1.75 (Kidney Donor Profile Index ≤85) was less pronounced for nonlocal offers (odds ratio, 0.82; 95% confidence interval, 0.80 to 0.85; P<0.001) and not significant for local offers.

The acceptability of marginal organs was higher when placements were nearer to the donor and when cold ischemia time was shorter.

减少丢弃对于美国移植系统非常重要，因为近 20% 的死亡供体肾脏被丢弃。丢弃的原因之一是避免长时间的冷缺血时间。移植时冷缺血时间延长与移植失败和患者死亡的额外风险相关。对本地（同一供体服务区域内）或低肾脏供体风险指数器官的偏好、器官分配期间冷缺血时间的内生性以及临时供体的使用都使冷缺血时间对肾脏接受影响的分析变得复杂决策。

使用 2018 年 1 月至 2019 年 6 月的器官采购和移植网络数据，我们对临时接受后接受肾脏报价的概率进行了建模。我们使用逻辑回归，其中包括冷缺血时间、肾脏捐赠者风险指数和从文献中选择的其他协变量。通过两阶段工具变量方法处理冷缺血时间的内生性。

来自 12,369 名捐赠者和 108,313 名候选人的 333 万份临时接受的逻辑回归结果量化了接受捐赠时的冷缺血时间与捐赠者-接受者特征之间的权衡。总体而言，冷缺血时间每增加 2 小时，就会影响非本地和本地受者的接受程度（比值比，0.75；95% 置信区间，0.73 至 0.77，比值比，0.88；95% 置信区间，0.86 至 0.91；P < 0.001） 。对于肾脏捐赠者风险指数 >1.75（肾脏捐赠者概况指数 >85）的肾脏，非本地和本地受者额外 2 小时的冷缺血时间与接受程度相关，比值比为 0.58；95% 置信区间，0.54 至 0.63（非局部），比值比，0.65；95% 置信区间，0.6 至 0.7（局部）；P <0.001。对于非本地提供的肾脏，额外 2 小时的冷缺血时间对接受肾脏捐赠者风险指数≤1.75（肾脏捐赠者概况指数≤85）的影响不太明显（优势比，0.82；95% 置信区间，0.80 至 0.85） ; P <0.001），对于本地优惠并不显着。

当放置位置离供体越近、冷缺血时间越短时，边缘器官的可接受性越高。