Predictors of Deceased Donor Kidney Discard in the United States

Clinical and Histologic Risk Factors for the Development of Early Allograft Dysfunction in Donation After Circulatory Death Kidney Transplantation

Transplantation of kidneys from donors after circulatory death (DCD) may help address the severe shortage of donor organs. However, they remain underutilized due to concerns for increased rates of delayed graft function (DGF) and primary nonfunction (PNF), despite similar long-term patient and allograft outcomes compared to kidneys from donors after brain death (DBD). Kidneys that recover from DGF have good long-term outcomes compared to those resulting in PNF. Considering immediate graft function (IGF), DGF, and PNF as a spectrum of renal allograft injury and recovery, we analyzed donor and recipient characteristics and corresponding time-zero biopsy findings for adult DCD kidney transplants at our center from 2016 to 2021. We compared transplants resulting in DGF with subsequent allograft recovery compared to those progressing to PNF as well as to grafts that functioned immediately. We found 344 patients received DCD kidneys with 153 resulting in DGF with renal recovery by 90-days post-transplant. Excluding surgical complications, 22 patients developed PNF and required ongoing maintenance dialysis after 90-days post-transplant and 169 patients had immediate graft function. Kidney Donor Profile Index ≥85% and donor history of diabetes and hypertension were associated with PNF. Cold and warm ischemia time, donor acute kidney injury, and use of hypothermic machine perfusion were not significantly different between the groups. Formalin-fixed paraffin embedded renal allograft time-zero biopsies demonstrated that increasing severity of donor-derived vascular disease present at the time of transplant were associated with the development of early allograft failure. These findings help define clinical characteristics important in kidney allograft selection.

Clinical characteristics and prediction model of re-positive nucleic acid tests among Omicron infections by machine learning: a real-world study of 35,488 cases

BACKGROUND

During the Omicron BA.2 variant outbreak in Shanghai, China, from April to May 2022, PCR nucleic acid test re-positivity (TR) occurred frequently, yet the risk factors and predictive models for TR remain unclear. This study aims to identify the factors influencing Omicron TR and to develop machine learning models to predict TR risk. Accurately predicting re-positive patients is crucial for identifying high-risk individuals, optimizing resource allocation, and developing personalized treatment and management plans, thereby effectively controlling the spread of the epidemic, reducing community burden, and ensuring public health.

METHODS

A retrospective study was conducted among individuals infected with Omicron BA.2 variant from April 12 to May 25, 2022, in the largest Shanghai Fangcang shelter hospital. Five machine learning models were compared, including k-nearest-neighbors (KNN), logistic regression (logistic), bootstrap aggregation (bagging), error back-propagation (BP) neural network, and support vector machines (SVM), to select the best prediction model for the TR risk factors.

RESULTS

A total of 35,488 cases were included in this real-world study. The TR and control groups comprised of 6,171 and 29,317 cases respectively, with a re-positive rate of 17.39%. Higher occurrence of TR was observed in young age, males, those with obvious symptoms, underlying diseases, and a low Ct value. The KNN model proved to be the best in predicting the prognosis in the overall evaluation (accuracy = 0.8198, recall = 0.8026, and AUC = 0.8110 in the test set).

INTERPRETATION

Higher TR risk was found in infected cases who were underage or with underlying diseases; vaccine brand and inoculation status were not significantly associated with TR. KNN was the most effective machine learning model to predict TR occurrence in isolation.

Kidney transplants from elderly donors: what we have learned 20 years after the Crystal City consensus criteria meeting

Based on the current projection of the general population and the combined increase in end-stage kidney disease with age, the number of elderly donors and recipients is increasing, raising crucial questions about how to minimize the discard rate of organs from elderly donors and improve graft and patient outcomes. In 2002, extended criteria donors were the focus of a meeting in Crystal City (VA, USA), with a goal of maximizing the use of organs from deceased donors. Since then, extended criteria donors have progressively contributed to a large number of transplanted grafts worldwide, posing specific issues for allocation systems, recipient management, and therapeutic approaches. This review analyzes what we have learned in the last 20 years about extended criteria donor utilization, the promising innovations in immunosuppressive management, and the molecular pathways involved in the aging process, which constitute potential targets for novel therapies.

Individualized empirical null estimation for exact tests of healthcare quality

United States federal agencies evaluate healthcare providers to identify, flag, and potentially penalize those that deliver low-quality care compared to national expectations. In practice, evaluation metrics are inevitably impacted by unobserved confounding factors, which reduce flagging accuracy and cause the statistics to be overdispersed relative to the theoretical null distributions. In response to this issue, several authors have proposed individualized empirical null (IEN) methods to estimate an appropriate null distribution for each provider's evaluation statistic while taking into account the provider's effective size. However, existing IEN methods require that the statistics asymptotically follow normal distributions, which often does not hold in applications with small providers or misspecified models. In this article, we develop an IEN framework for exact hypothesis tests that accounts for the impact of unobserved confounding without making any asymptotic assumptions. Simulations show that the proposed IEN method has greater flagging accuracy compared to conventional approaches. We apply these methods to evaluate dialysis facilities and transplant centers that are monitored by the Centers for Medicare and Medicaid Services.

The Kidney Not Taken: Single-Kidney Use in Deceased Donors

BACKGROUND

The nonuse rate for kidneys recovered from deceased donors is increasing, rising to 27% in 2023. In 10% of these cases, 1 kidney is transplanted but the mate kidney is not.

STUDY DESIGN

We conducted a retrospective, single-center cohort study from December 2001 to May 2023 comparing single kidneys transplanted at our center (where the contralateral kidney was not used) to kidneys where both were transplanted separately, at least 1 of which was at our center.

RESULTS

We performed 395 single deceased-donor kidney transplants in which the mate kidney was not transplanted. Primary reasons for mate kidney nonuse were as follows: no recipient located or list exhausted (33.4%), kidney trauma or injury or anatomic abnormalities (18.7%), biopsy findings (16.7%), and poor renal function (13.7%). Mean donor and recipient ages were 51.5 ± 14.2 and 60 ± 12.6 years, respectively. Mean kidney donor profile index was 73% ± 22%, and 104 donors (26.3%) had kidney donor profile index >85%. Mean cold ischemia was 25.6 ± 7.4 hours, and 280 kidneys (70.7%) were imported. Compared with 2,303 concurrent control transplants performed at our center, primary nonfunction or thrombosis (5.1% single vs 2.8% control) and delayed graft function (35.4% single vs 30.1% control) were greater with single-kidney use (both p < 0.05). Median patient and death-censored graft survival were shorter in the single group (11.6 vs 13.5 years, p = 0.03 and 11.6 vs 19 years, p = 0.003), although the former was at least double median survival on the waiting list. In patients with functioning grafts in the single-kidney group, 1-year mean serum creatinine was 1.77 ± 0.8 mg/dL and estimated glomerular filtration rate was 44.8 ± 20 mL/min/1.73 m 2 .

CONCLUSIONS

These findings suggest that many mate kidneys are being inappropriately rejected, given the acceptable outcomes that can be achieved by transplanting the single kidney in appropriately selected recipients.

COMPOSITE SCORES FOR TRANSPLANT CENTER EVALUATION: A NEW INDIVIDUALIZED EMPIRICAL NULL METHOD

Risk-adjusted quality measures are used to evaluate healthcare providers with respect to national norms while controlling for factors beyond their control. Existing healthcare provider profiling approaches typically assume that the between-provider variation in these measures is entirely due to meaningful differences in quality of care. However, in practice, much of the between-provider variation will be due to trivial fluctuations in healthcare quality, or unobservable confounding risk factors. If these additional sources of variation are not accounted for, conventional methods will disproportionately identify larger providers as outliers, even though their departures from the national norms may not be "extreme" or clinically meaningful. Motivated by efforts to evaluate the quality of care provided by transplant centers, we develop a composite evaluation score based on a novel individualized empirical null method, which robustly accounts for overdispersion due to unobserved risk factors, models the marginal variance of standardized scores as a function of the effective sample size, and only requires the use of publicly-available center-level statistics. The evaluations of United States kidney transplant centers based on the proposed composite score are substantially different from those based on conventional methods. Simulations show that the proposed empirical null approach more accurately classifies centers in terms of quality of care, compared to existing methods.

Prediction of High-Risk Donors for Kidney Discard and Nonrecovery Using Structured Donor Characteristics and Unstructured Donor Narratives

IMPORTANCE

Despite the unmet need, many deceased-donor kidneys are discarded or not recovered. Inefficient allocation and prolonged ischemia time are contributing factors, and early detection of high-risk donors may reduce organ loss.

OBJECTIVE

To evaluate the feasibility of machine learning (ML) and natural language processing (NLP) classification of donors with kidneys that are used vs not used for organ transplant.

DESIGN, SETTING, AND PARTICIPANTS

This retrospective cohort study used donor information (structured donor characteristics and unstructured donor narratives) from the United Network for Organ Sharing (UNOS). All donor offers to a single transplant center between January 2015 and December 2020 were used to train and validate ML models to predict donors who had at least 1 kidney transplanted (at our center or another center). The donor data from 2021 were used to test each model.

EXPOSURES

Donor information was provided by UNOS to the transplant centers with potential transplant candidates. Each center evaluated the donor and decided within an allotted time whether to accept the kidney for organ transplant.

MAIN OUTCOMES AND MEASURES

Outcome metrics of the test cohort included area under the receiver operating characteristic curve (AUROC), F1 score, accuracy, precision, and recall of each ML classifier. Feature importance and Shapley additive explanation (SHAP) summaries were assessed for model explainability.

RESULTS

The training/validation cohort included 9555 donors (median [IQR] age, 50 [36-58] years; 5571 male [58.3%]), and the test cohort included 2481 donors (median [IQR] age, 52 [40-59] years; 1496 male [60.3%]). Only 20% to 30% of potential donors had at least 1 kidney transplanted. The ML model with a single variable (Kidney Donor Profile Index) showed an AUROC of 0.69, F1 score of 0.42, and accuracy of 0.64. Multivariable ML models based on basic a priori structured donor data showed similar metrics (logistic regression: AUROC = 0.70; F1 score = 0.42; accuracy = 0.62; random forest classifier: AUROC = 0.69; F1 score = 0.42; accuracy = 0.64). The classic NLP model (bag-of-words model) showed its best metrics (AUROC = 0.60; F1 score = 0.35; accuracy = 0.59) by the logistic regression classifier. The advanced Bidirectional Encoder Representations From Transformers model showed comparable metrics (AUROC = 0.62; F1 score = 0.39; accuracy = 0.69) only after appending basic donor information. Feature importance and SHAP detected the variables (and words) that affected the models most.

CONCLUSIONS AND RELEVANCE

Results of this cohort study suggest that models using ML can be applied to predict donors with high-risk kidneys not used for organ transplant, but the models still need further elaboration. The use of unstructured data is likely to expand the possibilities; further exploration of new approaches will be necessary to develop models with better predictive metrics.

Deceased donor kidneys from higher distressed communities are significantly less likely to be utilized for transplantation

The proportion of kidneys procured for transplantation but not utilized exceeds 20% in the United States. Factors associated with nonutilization are complex, and further understanding of novel causes are critically important. We used the national Scientific Registry of Transplant Recipients data (2010-2022) to evaluate associations of Distressed Community Index (DCI) of deceased donor residence and likelihood of kidney nonutilization (n = 209 413). Deceased donors from higher distressed communities were younger, had an increased history of hypertension and diabetes, were CDC high-risk, and had higher terminal creatinine and donation after brain death. Mechanisms and circumstances of death varied significantly by DCI. The proportion of kidney nonutilization was 19.9%, which increased by DCI quintile (Q1 = 18.1% to Q5 = 21.6%). The adjusted odds ratio of nonutilization from the highest quintile DCI communities was 1.22 (95% CI = 1.16-1.28; reference = lowest DCI), which persisted stratified by donor race. Donors from highly distressed communities were highly variable by the donor service area (range: 1%-51%; median = 21%). There was no increased risk for delayed graft function or death-censored graft loss by donor DCI but modest increased adjusted hazard for overall graft loss (high DCI = 1.05; 95% CI = 1.01-1.10; reference = lowest DCI). Results indicate that donor residential distress is associated with significantly higher rates of donor kidney nonutilization with notable regional variation and minimal impact on recipient outcomes.

Donors With a Prior History of Cancer: Factors of Non-Utilization of Kidneys for Transplantation

Cancer transmission from deceased donors is an exceedingly rare but potentially fatal complication in transplant recipients. We aimed to quantify the likelihood of non-utilization of kidneys for transplantation from donors with a prior cancer history. We included all intended and actual deceased donors in Australia and New Zealand between 1989 and 2017. Association between prior cancer history and non-utilization of donor kidneys was examined using adjusted logistic regression. Of 9,485 deceased donors, 345 (4%) had a prior cancer history. Of 345 donors with a prior cancer history, 197 (57%) were utilized for transplantation. Donor characteristics of age, sex and comorbidities were similar between utilized and non-utilized donors with prior cancer. The time from cancer to organ donation was similar between utilized and non-utilized donors, irrespective of cancer subtypes. Donors with a prior cancer history were less likely to be utilized [adjusted OR (95% CI) 2.29 (1.68-3.13)] than donors without prior cancer. Of all actual donors, the adjusted OR for non-utilization among those with prior cancer was 2.36 (1.58-3.53). Non-melanoma skin cancer was the most frequent prior cancer type for utilized and non-utilized potential donors. Donors with prior cancers were less likely to be utilized for transplantation, with no discernible differences in cancer characteristics between utilized and non-utilized donors.

Single center experience and literature review of kidney transplantation from non-ideal donors with acute kidney injury: Risk and reward

INTRODUCTION

There is limited experience transplanting kidneys from either expanded criteria donors (ECD) or donation after circulatory death (DCD) deceased donors with terminal acute kidney injury (AKI).

METHODS

AKI kidneys were defined by a donor terminal serum creatinine level >2.0 mg/dL whereas non-ideal deceased donor (NIDD) kidneys were defined as AKI/DCD or AKI/ECDs.

RESULTS

From February 2007 to March 2023, we transplanted 266 single AKI donor kidneys including 29 from ECDs, 29 from DCDs (n = 58 NIDDs), and 208 from brain-dead standard criteria donors (SCDs). Mean donor age (43.7 NIDD vs. 33.5 years SCD), KDPI (66% NIDD vs. 45% SCD), and recipient age (57 NIDD vs. 51 years SCD) were higher in the NIDD group (all p < .01). Mean waiting times (17.8 NIDD vs. 24.2 months SCD) and dialysis duration (34 NIDD vs. 47 months SCD) were shorter in the NIDD group (p < .05). Delayed graft function (DGF, 48%) and 1-year graft survival (92.7% NIDD vs. 95.9% SCD) was similar in both groups. Five-year patient and kidney graft survival rates were 82.1% versus 89.9% and 82.1% versus 75.2% (both p = NS) in the NIDD versus SCD groups, respectively.

CONCLUSIONS

The use of kidneys from AKI donors can be safely liberalized to include selected ECD and DCD donors.

Long-term outcomes of kidney transplantation from deceased donors with terminal acute kidney injury: Single center experience and literature review

INTRODUCTION

Long-term outcomes of kidney transplantation from deceased donors (DDKTs) with terminal acute kidney injury (AKI) are not well defined.

METHODS

Single center retrospective review of DDKTs from 1/31/07-12/31/19. AKI kidneys were defined by a doubling of the donor's admission serum creatinine (SCr) level AND a terminal SCr ≥2.0 mg/dl.

RESULTS

A total of 188 AKI DDKTs were performed, including 154 from brain-dead standard criteria donors (SCD). Mean donor age was 36 years and mean Kidney Donor Profile Index was 50%; mean admission and terminal SCr levels were 1.3 and 3.1 mg/dl, respectively. With a mean follow-up of 94 months (median 89 months), overall patient (both 71.3%) and graft survival (54% AKI vs. 57% non-AKI) rates were comparable to concurrent DDKTs from brain-dead non-AKI SCDs (n = 769). Delayed graft function (DGF) was higher in AKI kidney recipients (47% vs. 20% non-AKI DDKTs, p < .0001). DGF was associated with lower graft survival in recipients of both AKI and non-AKI SCD kidneys but the impact was earlier and more pronounced in non-AKI recipients.

CONCLUSIONS

Despite having more than twice the incidence of DGF, kidneys from deceased donors with terminal AKI have long-term outcomes comparable to non-AKI SCD kidneys and represent a safe and effective method to expand the donor pool.

Identify Hard-to-Place Kidneys for Early Engagement in Accelerated Placement With a Deep Learning Optimization Approach

Recommended practices that follow match-run sequences for hard-to-place kidneys succumb to many declines, accruing cold ischemic time and exacerbating kidney quality that may lead to unnecessary kidney discard. Hard-to-place deceased donor kidneys accepted and transplanted later in the match-run sequence may threaten higher graft failure rates. Accelerated placement is a practice for organ procurement organizations (OPOs) to allocate high-risk kidneys out of sequence and reach patients at aggressive transplant centers. The current practice of assessing hard-to-place kidneys and engaging in accelerated kidney placements relies heavily on the kidney donor profile index (KDPI) and the number of declines. Although this practice is reasonable, it also accrues cold ischemic time and increases the risk for kidney discard. We use a deep learning optimization approach to quickly identify kidneys at risk for discard. This approach uses Organ Procurement and Transplantation Network data to model kidney disposition. We filter discards and develop a model to predict transplant and discard of recovered and not transplanted kidneys. Kidneys with a higher probability of discard are deemed hard-to-place kidneys, which require early engagement for accelerated placement. Our approach will aid in identifying hard-to-place kidneys before or after procurement and support OPOs to deviate from the match-run for accelerated placement. Compared with the KDPI-only prediction of the kidney disposition, our approach demonstrates a 10% increase in correctly predicting kidneys at risk for discard. Future work will include developing models to identify candidates with an increased benefit from using hard-to-place kidneys.

Impact of belatacept and tacrolimus on cytomegalovirus viral load control and relapse in moderate and high-risk cytomegalovirus serostatus kidney transplant recipients

BACKGROUND

Belatacept improves long-term graft survival, but control of some primary viral infections may be impaired. We evaluated the impact of belatacept and tacrolimus on cytomegalovirus (CMV) viral control, remission and relapse in CMV high-risk and moderate-risk recipients.

METHODS

Using a multistate Markov model, we evaluated viral load state transitions of 173 kidney transplant recipients with at least one episode of viremia within 1 year after transplant: state 1, undetectable/low viral load; state 2, moderate viremia; and state 3, severe viremia.

RESULTS

Among high-risk recipients, belatacept-treated recipients exhibited a significantly higher probability of entering moderate viremia (.36; 95% CI = .31, .41) than tacrolimus-treated recipients (.20; 95% CI = .13, .29). The expected number of days in viremic states differed. High-risk belatacept-treated recipients persisted in moderate viremia for significantly longer (128 days, 95% CI = 110, 146) than did tacrolimus-treated recipients (70.0 days, 95% CI = 45.2, 100) and showed a trend of shorter duration in low/undetectable viral load state (172 days, 95% CI = 148, 195) than did tacrolimus-treated recipients (239 days, 95% CI = 195, 277). Moderate-risk recipients showed better viral load control and with no differences by immunosuppression.

CONCLUSION

High-risk belatacept-treated recipients showed defects in sustaining viral control relative to tacrolimus-treated recipients. Avoidance of initial use belatacept in high-risk recipients or development of modified management protocols should be considered.

Kidney utilization in the Netherlands - do we optimally use our donor organs?

BACKGROUND

To ensure optimal utilization of deceased donor kidneys, it is important to understand the precise reasons why kidneys are discarded. In this study we aimed to obtain a comprehensive overview of kidney utilization and discard during the entire donation process in the Netherlands.

METHODS

In this retrospective cohort study we analysed kidney utilization of 3856 kidneys in the Netherlands between 1 January 2015 and 31 December 2020. For every kidney that was not transplanted, we determined the moment of and reason for discard through a unique case-by-case assessment.

RESULTS

Kidney discard according to the traditional definition (procured but not transplanted) was 7.8%. However, when kidneys that seemed medically suitable at the beginning of the donation process were also included, many more potential donor kidneys were lost and the total non-utilization was 24.4%. Subjectively presumed impaired organ quality was responsible for 34.2% of all discarded kidneys. Two-thirds of kidneys discarded due to acute kidney injury (AKI) had only AKI stage 1 or 2.

CONCLUSION

The classical definition of organ discard underestimates the non-utilization of deceased donor kidneys. Strategies to improve kidney utilization could be a revision of the maximum allowed agonal time in donation after circulatory death, careful consideration in reporting and accepting kidneys from donors with AKI and a prospectively filled registry of detailed organ discard reasons, including the 'silent' non-utilization before procurement.

The Independent Effects of Procurement Biopsy Findings on Ten-Year Outcomes of Extended Criteria Donor Kidney Transplants

Introduction

Methods

Results

Conclusion

Computer-assisted evaluation enhances the quantification of interstitial fibrosis in renal implantation biopsies, measures differences between frozen and paraffin sections, and predicts delayed graft function

Background

(Pre-)Implantation biopsies provide important data on the quality of donor kidneys. Interstitial fibrosis, as a known predictor for kidney disease progression, is an essential feature of this evaluation. However, the assessment of frozen sections of implantation biopsies is challenging and can result in the disposal of candidate organs. We sought to apply digital image analysis (DIA) to quantify the differences between frozen and paraffin sections when evaluating interstitial fibrosis, identify factors that influence these variations and test the predictive value of the computerised measures.

Methods

We quantified the differences between frozen and paraffin sections in the same biopsy samples by measuring Sirius red-stained interstitial areas (SRIA) in DIA. We compared them to the original reports, and retrospectively correlated our findings to clinical data, graft function and outcome in 73 patients.

Results

Frozen sections display a broader interstitial area than paraffin sections, in some cases up to one-third more (mean difference + 7.8%, range − 7 to 29%). No donor-related factors (age or gender, cold ischemia time, or non-heart-beating donor) influenced significantly this difference. Compared to the original assessment of frozen vs paraffin sections in optical microscopy, the DIA of interstitial fibrosis shows a higher consistency (ICC 0.69). Our approach further allows to distinguish SRIA in paraffin sections as an independent predictor for delayed graft function (OR = 1.1; p = 0.028).

Conclusions

DIA is superior to and more consistent than routine optic microscopy for interstitial fibrosis evaluation. This method could improve implantation biopsy diagnostics and help to reduce disposal of organs.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s40620-022-01315-y.

Kidney transplant outcome of expanded criteria donors after circulatory death

The increase in the number of patients on the kidney transplant waiting list has led to an attempt to increase the number of potential donors by incorporating candidates that previously would not have been considered optimal, including donors after cardiac death (DCD) and those with "expanded" criteria (ECD). Recipients of controlled DCD (cDCD) grafts suffer more delayed graft function (DGF), but have a long-term evolution comparable to those of brain-dead donors, which has allowed an increase in the number of cDCD transplants in different countries in recent years. In parallel, the use of cDCD with expanded criteria (cDCD/ECD) has increased in recent years in different countries, allowing the waiting list for kidney transplantation to be shortened. The use of these grafts, although associated with a higher frequency of DGF, offers similar or only slightly lower long-term graft survival than those of brain death donors with expanded criteria. Different studies have observed that cDCD/ECD graft recipients have worse kidney function than cDCD/standard and DBD/ECD. Mortality associated with cDCD/ECD graft transplantation mostly relates to the recipient age. Patients who receive a cDCD/≥60 graft have better survival than those who continue on the waiting list, although this fact has not been demonstrated in recipients of cDCD/>65 years. The use of this type of organ should be accompanied by the optimization of surgical times and the shortest possible cold ischemia.

The use of marginal kidneys in dual kidney transplantation to expand kidney graft utilization

PURPOSE OF REVIEW

The purpose of this review is to chronicle the history of dual kidney transplantation (DKT) and identify opportunities to improve utilization of marginal deceased donor (MDD) kidneys through DKT.

RECENT FINDINGS

The practice of DKT from adult MDDs dates back to the mid-1990s, at which time the primary indication was projected insufficient nephron mass from older donors. Multiple subsequent studies of short- and long-term success have been reported focusing on three major aspects: Identifying appropriate selection criteria/scoring systems based on pre- and postdonation factors; refining technical aspects; and analyzing longer-term outcomes. The number of adult DKTs performed in the United States has declined in the past decade and only about 60 are performed annually. For adult deceased donor kidneys meeting double allocation criteria, >60% are ultimately not transplanted. MDDs with limited renal functional capacity represent a large proportion of potential kidneys doomed to either discard or nonrecovery.

SUMMARY

DKT may reduce organ discard and optimize the use of kidneys from MDDs. New and innovative technologies targeting ex vivo organ assessment, repair, and regeneration may have a major impact on the decision whether or not to use recovered kidneys for single or DKT.

Dual kidney transplants from adult marginal donors: Review and perspective

The practice of dual kidney transplantation (DKT) from adult marginal deceased donors (MDDs) dates back to the mid-1990s with initial pioneering experiences reported by the Stanford and Maryland groups, at which time the primary indication was estimated insufficient nephron mass from older donors. Multiple subsequent studies of short and long-term success have been reported focusing on three major aspects of DKT: Identifying appropriate selection criteria and developing scoring systems based on pre- and post-donation factors; refining technical aspects; and analyzing mid-term outcomes. The number of adult DKTs performed in the United States has declined in the past decade and only about 60 are performed annually. For adult deceased donor kidneys meeting double allocation criteria, >60% are ultimately not transplanted. Deceased donors with limited renal functional capacity represent a large proportion of potential kidneys doomed to either discard or non-recovery. However, DKT may reduce organ discard and optimize the use of kidneys from MDDs. In an attempt to promote utilization of MDD kidneys, the United Network for Organ Sharing introduced new allocation guidelines pursuant to DKT in 2019. The purpose of this review is to chronicle the history of DKT and identify opportunities to improve utilization of MDD kidneys through DKT. This article is protected by copyright. All rights reserved.

Role of deceased donor kidney procurement biopsies in organ allocation

PURPOSE OF REVIEW

There has been an increased emphasis by the transplant community and the federal government to increase the utilization of deceased donor kidneys. Procurement biopsies during allocation are the most common reason for kidney discards. This manuscript reviews the evidence of procurement biopsies practices and utility.

RECENT FINDINGS

Procurement biopsies are performed in over half of all the kidneys recovered in the United States and account for more than one third of the kidney discards. However, there is a significant heterogeneity across the organ procurement organizations regarding the indications for biopsy, biopsy techniques and their reporting. Procurement biopsy findings are not reproducible and poorly correlate to postimplantation histology, although reasons for these limitations are not clear. Procurement biopsy findings are not associated with posttransplant outcomes after accounting for readily available donor clinical characteristics.

SUMMARY

Procurement biopsies contribute to deceased donor kidney discards but do not predict posttransplant outcomes. Research to establish the best practices for procurement biopsies is needed to improve organ utilization.

Hardest-to-place kidney transplant outcomes in the United States

The outcomes of hardest-to-place kidney transplants-accepted last in the entire match run after being refused by previous centers-are unclear, potentially translating to risk aversion and unnecessary organ discard. We aimed to determine the outcomes of hardest-to-place kidney transplants and whether the organ acceptance position on the match run sufficiently captures the risk. This is a cohort study of the United Network for Organ Sharing data of all adult kidney-only transplant recipients from deceased donors between 2007 and 2018. Multiple regression models assessed delayed graft function, graft survival, and patient survival stratified by share type: local versus shared kidney acceptance position scaled by tertile. Among 127 028 kidney transplant recipients, 92 855 received local kidneys. The remaining received shared kidneys at sequence number 1-4 (n = 12 322), 5-164 (n = 10 485) and >164 (n = 11 366). Hardest-to-place kidneys, defined as the latest acceptance group in the match-run, were associated with delayed graft function (adjusted odds ratio 1.83, 95% confidence interval [CI] 1.74-1.92) and all-cause allograft failure (adjusted hazard ratio [aHR] 1.11, 95% CI 1.04-1.17). Results of this IRB-approved study were robust to the exclusion of operational allocation bypass and mandatory shares. The hardest-to-place kidneys accepted later in the match run were associated with higher graft failure and delayed graft function.

Predicting Kidney Discard Using Machine Learning

BACKGROUND

Despite the kidney supply shortage, 18%-20% of deceased donor kidneys are discarded annually in the United States. In 2018, 3569 kidneys were discarded.

METHODS

We compared machine learning (ML) techniques to identify kidneys at risk of discard at the time of match run and after biopsy and machine perfusion results become available. The cohort consisted of adult deceased donor kidneys donated between December 4, 2014, and July 1, 2019. The studied ML models included Random Forests (RF), Adaptive Boosting (AdaBoost), Neural Networks (NNet), Support Vector Machines (SVM), and K-nearest Neighbors (KNN). In addition, a Logistic Regression (LR) model was fitted and used for comparison with the ML models' performance.

RESULTS

RF outperformed other ML models. Of 8036 discarded kidneys in the test dataset, LR correctly classified 3422 kidneys, whereas RF correctly classified 4762 kidneys (area under the receiver operative curve [AUC]: 0.85 versus 0.888, and balanced accuracy: 0.681 versus 0.759). For the kidneys with kidney donor profile index of >85% (6079 total), RF significantly outperformed LR in classifying discard and transplant prediction (AUC: 0.814 versus 0.717, and balanced accuracy: 0.732 versus 0.657). More than 388 kidneys were correctly classified using RF. Including biopsy and machine perfusion variables improved the performance of LR and RF (LR's AUC: 0.888 and balanced accuracy: 0.74 versus RF's AUC: 0.904 and balanced accuracy: 0.775).

CONCLUSIONS

Kidneys that are at risk of discard can be more accurately identified using ML techniques such as RF.

US deceased kidney transplantation: Estimated GFR, donor age and KDPI association with graft survival

BACKGROUND

Despite a significant shortage of kidneys for transplantation in the US, kidneys from older deceased donors are infrequently transplanted. This is primarily over concern of graft quality and transplant durability.

METHODS

The US national transplant database (2000-2018) was assessed for deceased donor kidney transplant patient and graft survival, graft durability and stratified by donor age (<65 years>), Kidney Donor Profile Index (KDPI) and estimated glomerual filtration rate (GFR) one year post-transplantation (eGFR-1) were calculated.

FINDINGS

Recipients of kidneys transplanted from deceased donors >65 years had a lower eGFR-1, (median 39 ml/min) than recipients of younger donor kidneys (median 54 ml/min). However, death-censored graft survival, stratified by eGFR-1, demonstrated similar survival, irrespective of donor age or KDPI. The durability of kidney survival decreases as the achieved eGFR-1 declines. KDPI has a poor association with eGFR-1 and lesser for graft durability. While recipients of kidneys > 65 years had a higher one year mortality than younger kidney recipients, recipients of kidneys > 65 years and an eGFR-1 <30 ml/min, had a lower survival than an untransplanted waitlist cohort (p<0.001).

INTERPRETATION

The durability of kidney graft survival after transplantation was associated with the amount of kidney function gained through the transplant (eGFR-1) and the rate of graft loss (return to dialysis) was not significantly associated with donor age. 24.9% of recipients of older donor kidneys failed to achieve sufficient eGFR-1 providing a transplant survival benefit. While there is significant benefit from transplanting older kidneys, better decision-making tools are required to avoid transplanting kidneys that provide insufficient renal function.

FUNDING

None.

Kidney transplant outcome of expanded criteria donors after circulatory death

The increase in the number of patients on the kidney transplant waiting list has led to an attempt to increase the number of potential donors by incorporating candidates that previously would not have been considered optimal, including donors after cardiac death (DCD) and those with "expanded" criteria (ECD). Recipients of controlled DCD (cDCD) grafts suffer more delayed graft function (DGF), but have a long-term evolution comparable to those of brain-dead donors, which has allowed an increase in the number of cDCD transplants in different countries in recent years. In parallel, the use of cDCD with expanded criteria (cDCD/ECD) has increased in recent years in different countries, allowing the waiting list for kidney transplantation to be shortened. The use of these grafts, although associated with a higher frequency of DGF, offers similar or only slightly lower long-term graft survival than those of brain death donors with expanded criteria. Different studies have observed that cDCD/ECD graft recipients have worse kidney function than cDCD/standard and brain death/ECD. Mortality associated with cDCD/ECD graft transplantation mostly relates to the recipient age. Patients who receive a cDCD/≥60 graft have better survival than those who continue on the waiting list, although this fact has not been demonstrated in recipients of cDCD/>65 years. The use of this type of organ should be accompanied by the optimization of surgical times and the shortest possible cold ischemia.

Impact of acute kidney injury in deceased donors with high Kidney Donor Profile Index on posttransplant clinical outcomes: a multicenter cohort study

BACKGROUND

This study evaluated the impact of acute kidney injury (AKI) on posttransplant clinical outcomes for deceased donor (DD) kidney transplantation (KT) using the Kidney Donor Profile Index (KDPI) system.

METHODS

Overall, 657 kidney transplant recipients (KTRs) receiving kidneys from 526 DDs from four transplant centers were included. We divided them into the high and low KDPI donor groups by 65%, the KDPI score, and both groups were subdivided into the AKI-DDKT and non-AKI-DDKT subgroups according to AKI in DDs.

RESULTS

There was no significant difference in the incidence of delayed graft function (DGF) between the high and low KDPI-KTR groups; however, the AKI-DDKT subgroup showed significantly higher incidence of DGF than the non-AKI-DDKT subgroup in both groups (p = 0.001, p < 0.001, respectively). The death-censored graft survival rate was significantly lower in the high KDPI-KTR group than in the low KDPI-KTR group (p = 0.005). Only in the high KDPI-KTR group, the death-censored graft survival rate was significantly lower in the KT from DDs with AKI stage 3 than KT from DDs with non-AKI or AKI stage 1 or 2 (p = 0.040). The interaction between AKI stage 3 in DDs and high KDPI on the allograft outcome was significant (p = 0.002).

CONCLUSION

KTs from DDs with AKI stage 3 showed an adverse impact on the allograft outcome in the high KDPI-KTR group. Therefore, DDs with a high KDPI score should be managed carefully so that severe AKI does not occur prior to KT.

Prediction of Kidney Allograft Discard Before Procurement: The Kidney Discard Risk Index

OBJECTIVES

There is an 18.9% discard rate among kidney allografts. Here, we aimed to determine predictors of kidney discard and construct an index to identify high-probability discard kidney allografts prior to procurement.

MATERIALS AND METHODS

A total of 102 246 potential kidney allograft donors from the Organ Procurement and Transplantation Network database were used in this analysis. The cohort was randomized into 2 groups. The training set included 67% of the cohort and was used to derive a predictive index for discard that comprised 21 factors identified by univariate and multivariate logistic regression analysis. The validation set included 33% and was used to internally validate the kidney discard risk index.

RESULTS

In 77.3% of donors, at least 1 kidney was used for transplant, whereas in 22.7% of donors, both kidneys were discarded. The kidney discard risk index was highly predictive of discard with a C statistic of 0.89 (0.88-0.89). The bottom 10th percentile had a discard rate of 0.73%, whereas the top 10th percentile had a discard rate of 83.65%. The 3 most predictive factors for discard were age, creatinine level, and hepatitis C antibody status.

CONCLUSIONS

We identified 21 factors predictive of discard prior to donor procurement and used these to develop a kidney discard risk index with a C statistic of 0.89.

Assessment of the Utility of Kidney Histology as a Basis for Discarding Organs in the United States: A Comparison of International Transplant Practices and Outcomes

BACKGROUND

Many kidneys donated for transplant in the United States are discarded because of abnormal histology. Whether histology adds incremental value beyond usual donor attributes in assessing allograft quality is unknown.

METHODS

This population-based study included patients who received a deceased donor kidney that had been biopsied before implantation according to a prespecified protocol in France and Belgium, where preimplantation biopsy findings are generally not used for decision making in the allocation process. We also studied kidneys that had been acquired from deceased United States donors for transplantation that were biopsied during allocation and discarded because of low organ quality. Using donor and recipient characteristics, we fit multivariable Cox models for death-censored graft failure and examined whether predictive accuracy (C index) improved after adding donor histology. We matched the discarded United States kidneys to similar kidneys transplanted in Europe and calculated predicted allograft survival.

RESULTS

In the development cohort of 1629 kidney recipients at two French centers, adding donor histology to the model did not significantly improve prediction of long-term allograft failure. Analyses using an external validation cohort from two Belgian centers confirmed the lack of improved accuracy from adding histology. About 45% of 1103 United States kidneys discarded because of histologic findings could be accurately matched to very similar kidneys that had been transplanted in France; these discarded kidneys would be expected to have allograft survival of 93.1% at 1 year, 80.7% at 5 years, and 68.9% at 10 years.

CONCLUSIONS

In this multicenter study, donor kidney histology assessment during allocation did not provide substantial incremental value in ascertaining organ quality. Many kidneys discarded on the basis of biopsy findings would likely benefit United States patients who are wait listed.

Kidney nonprocurement in solid organ donors in the United States

There are limited data on the nonprocurement of kidneys from solid organ donors. Analysis of Standard Transplant Analysis and Research files was undertaken on all deceased donors in the United States with at least 1 solid organ recovered. From 2000 to 2018, 21 731 deceased donor kidneys (averaging 1144 kidneys per year) were not procured. No kidneys were procured from 8% of liver donors, 3% of heart donors, and 3% of lung donors. Compared to donors with all kidneys procured, those with none procured were older and more likely obese, black, hypertensive, diabetic, hepatitis C positive, smokers, Public Health Service - Increased Risk designated, deceased after cardiac death, or deceased after cerebrovascular accident. Although these donors had lower quality kidneys (median Kidney Donor Risk Index (interquartile range) 1.9 (1.0) vs 1.2 (0.7)), there was substantial overlap in quality between nonprocured and procured kidneys. Nearly one third of nonprocurements were attributed to donor history. Donors with elevated terminal creatinine likely resulting from acute kidney injury (AKI) had higher odds of kidney nonprocurement. Nonprocurement odds varied widely across Organ Procurement and Transplantation Network regions, with a positive correlation between donor kidney nonprocurements and kidney discards at the donation service area level. These findings suggest current discard rates underestimate the underutilization of deceased donor kidneys and more research is needed to optimize safe procurement and utilization of kidneys from donors with AKI.

Urine Injury Biomarkers Are Not Associated With Kidney Transplant Failure

BACKGROUND

Kidneys transplanted from deceased donors with serum creatinine-defined acute kidney injury (AKI) have similar allograft survival as non-AKI kidneys but are discarded at a higher rate. Urine injury biomarkers are sensitive markers of structural kidney damage and may more accurately predict graft outcomes.

METHODS

In the 2010-2013 multicenter Deceased Donor Study of 2430 kidney transplant recipients from 1298 donors, we assessed the association of donor urine injury biomarkers microalbumin, neutrophil gelatinase-associated lipocalin, kidney injury molecule-1, IL-18, and liver-type fatty acid binding protein with graft failure (GF) and death-censored GF (dcGF) using Cox proportional hazard models (median follow-up 4 y). We examined if serum creatinine-defined donor AKI modified this association to assess the relationship between subclinical donor AKI (elevated biomarkers without creatinine-defined AKI) and GF. Through chart review of a subcohort (1137 recipients), we determined associations between donor injury biomarkers and a 3-year composite outcome of GF, mortality, or estimated glomerular filtration rate ≤ 20mL/min/1.73m.

RESULTS

Risk of GF, dcGF, and 3-year composite outcome did not vary with donor injury biomarker concentrations after adjusting for donor, transplant, and recipient characteristics (adjusted hazard ratio ranged from 0.96 to 1.01 per log-2 increase in biomarker). Subclinical injury in transplanted kidneys without AKI was not associated with GF.

CONCLUSIONS

AKI measured using injury biomarkers was not associated with posttransplant graft outcomes (at median 4 y posttransplant). When assessing posttransplant graft viability, clinicians can prioritize other donor and recipient factors over donor kidney injury, measured by either serum creatinine or urine injury biomarkers.

Utilization of Donor Kidneys With Acute Kidney Injury in Pediatric Kidney Transplant Recipients

BACKGROUND

An elevated terminal creatinine is frequently used as a reason for organ refusal in pediatric kidney transplantation. There is increasing evidence that adults who receive kidneys from donors with moderate to severe acute kidney injury (AKI) have similar outcomes to recipients who receive kidneys from donors with none to mild AKI.

METHODS

We used the Scientific Registry of Transplant Recipients to determine how many pediatric kidney transplant recipients developed delayed graft function (DGF) between 2000 and 2010.

RESULTS

When stratified by the donor terminal creatinine, there was no significant difference in the recipient discharge creatinine or the likelihood of developing DGF. In a logistic regression model, older donor age, male donors, and a longer cold ischemia time but not donor terminal creatinine were independent predictors of DGF. There were very few graft loss events documented in this study.

CONCLUSIONS

Our results are in agreement with previously published data; a high donor terminal creatinine is not significantly associated with DGF in pediatric renal transplant recipients. Additional studies investigating the risk of rejection and long-term graft function are needed before adopting the practice of accepting kidneys with moderate to severe AKI in pediatric kidney transplant recipients.

The cost of procuring deceased donor kidneys: Evidence from OPO cost reports 2013-2017

Using 5 years of US organ procurement organization (OPO) data, we determined the cost of recovering a viable (ie, transplanted) kidney for each of 51 OPOs. We also examined the effects on OPO costs of the recovery of nonviable (ie, discarded) kidneys and other OPO metrics. Annual cost reports from 51 independent OPOs were used to determine the cost per recovered kidney for each OPO. A quadratic regression model was employed to estimate the relationship between the cost of kidneys and the number of viable kidneys recovered, as well as other OPO performance indicators. The cost of transplanted kidneys at individual OPOs ranged widely from $24 000 to $56 000, and the average was $36 000. The cost of a viable kidney tended to decline with the number of kidneys procured up to 549 kidneys per year and then increase. Of the total 81 401 kidneys recovered, 66 454 were viable and 14 947 (18.4%) were nonviable. The costs of kidneys varied widely over the OPOs studied, and costs were a function of the recovered number of viable and nonviable organs, local cost levels, donation after cardiac death, year, and Standardized Donor Rate Ratio. Cost increases were 3% per year.

Can donor narratives yield insights? A natural language processing proof of concept to facilitate kidney allocation

Although expedited placement could ameliorate stagnant kidney utilization, precisely identifying difficult-to-place organs is crucial to mitigate potential harms associated with this policy. Existing algorithms have only leveraged structured data from the Organ Procurement and Transplantation Network (OPTN); however, detailed, free text case information about a donor exists. No known research exists about the utility of these data. We developed a model to predict the probability of delay or discard for adult deceased kidney donors between 2010 and 2018, leveraging donor free text data. The resultant model had a c-statistic of 0.75 compared to 0.80 ( Reduced Probability of Delay or Discard [model], r-PODD) and 0.77 ( Kidney Donor Profile Index, KDPI) on the test dataset. Analysis of the top predictive words suggest both known and potentially novel clinical factors (ie, a known factor such as hypertension vs a novel factor such as stents), and nuanced social factors (intravenous drug use) could negatively affect kidney utilization. These findings suggest that donor narratives have utility; the natural language processing (NLP) model is only moderately correlated with existing indices and provides directional evidence about additional cardiovascular risk factors that may affect kidney utilization. More research is needed to understand the potential to enhance existing indices of kidney utilization to better enable and mitigate the effects of policy interventions such as expedited placement.

Kidney Transplantation From Hepatitis B Surface Antigen (HBsAg)–Positive Living Donors to HBsAg-Negative Recipients: Clinical Outcomes at a High-Volume Center in China

Background

Data on kidney transplantation (KTx) from hepatitis B surface antigen (HBsAg)–positive (HBsAg+) donors to HBsAg-negative (HBsAg−) recipients [D(HBsAg+)/R(HBsAg-)] are limited. We aimed to report the outcomes of D(HBsAg+)/R(HBsAg−) KTx in recipients with or without hepatitis B surface antibody (HBsAb).

Methods

Eighty-three D(HBsAg+)/R(HBsAg−) living KTx cases were retrospectively identified. The 384 cases of KTx from hepatitis B core antibody–positive (HBcAb+) living donors to HBcAb-negative (HBcAb−) recipients [D(HBcAb+)/R(HBcAb−)] were used as the control group. The primary endpoint was posttransplant HBsAg status change from negative to postive (-− →+).

Results

Before KTx, 24 donors (28.9%) in the D(HBsAg+)/R(HBsAg−) group were hepatitis B virus (HBV) DNA positive, and 20 recipients were HBsAb−. All 83 D(HBsAg+)/R(HBsAg−) recipients received HBV prophylaxis, while no D(HBcAb+)/R(HBcAb−) recipients received prophylaxis. After a median follow-up of 36 months (range, 6–106) and 36 months (range, 4–107) for the D(HBsAg+)/R(HBsAg−) and D(HBcAb+)/R(HBcAb−) groups, respectively, 2 of 83 (2.41%) D(HBsAg+)/R(HBsAg−) recipients and 1 of 384 (0.26%) D(HBcAb+)/R(HBcAb−) became HBsAg+, accompanied by HBV DNA-positive (P = .083). The 3 recipients with HBsAg−→+ were exclusively HBsAb−/HBcAb− before KTx. Recipient deaths were more frequent in the D(HBsAg+)/R(HBsAg−) group (6.02% vs 1.04%, P = .011), while liver and graft function, rejection, infection, and graft loss were not significantly different. In univariate analyses, pretransplant HBsAb−/HBcAb− combination in the D(HBsAg+)/R(HBsAg−) recipients carried a significantly higher risk of HBsAg−→+, HBV DNA−→+, and death.

Conclusions

Living D(HBsAg+)/R(HBsAg−) KTx in HBsAb+ recipients provides excellent graft and patient survivals without HBV transmission. HBV transmission risks should be more balanced with respect to benefits of D(HBsAg+)/R(HBsAg−) KTx in HBsAb-/HBcAb− candidates.

Can Behavioral Research Improve Transplant Decision-Making? A Mock Offer Study on the Role of Kidney Procurement Biopsies

Background

The use of procurement biopsies for assessing kidney quality has been implicated as a driver of the nearly 20% kidney discard rate in the United States. Yet in some contexts, biopsies may boost clinical confidence, enabling acceptance of kidneys that would otherwise be discarded. We leveraged a novel organ offer simulation platform to conduct a controlled experiment isolating biopsy effects on offer acceptance decisions.

Methods

Between November 26 and December 14, 2018, 41 kidney transplant surgeons and 27 transplant nephrologists each received the same 20 hypothetical kidney offers using a crossover design with weekend "washout" periods. Mini-study 1 included four, low serum creatinine (<1.5 mg/dl) donor offers with arguably "poor" biopsy findings that were based on real offers that were accepted with successful 3-year recipient outcome. For each of the four offers, two experimental variants-no biopsy and "good" biopsy-were also sent. Mini-study 2 included four AKI offers with no biopsy, each having an offer variant with "good" biopsy findings.

Results

Among low serum creatinine donor offers, we found approximately threefold higher odds of acceptance when arguably poor biopsy findings were hidden or replaced with good biopsy findings. Among AKI donor offers, we found nearly fourfold higher odds of acceptance with good biopsy findings compared with no biopsy. Biopsy information had profound but variable effects on decision making: more participants appeared to have been influenced by biopsies to rule out, versus rule in, transplantable kidneys.

Conclusions

The current use of biopsies in the United States appears skewed toward inducing kidney discard. Several areas for improvement, including reducing variation in offer acceptance decisions and more accurate interpretation of findings, have the potential to make better use of scarce, donated organs. Offer simulation studies are a viable research tool for understanding decision making and identifying ways to improve the transplant system.

Reproducibility of Deceased Donor Kidney Procurement Biopsies

BACKGROUND AND OBJECTIVES

Unfavorable histology on procurement biopsies is the most common reason for deceased donor kidney discard. We sought to assess the reproducibility of procurement biopsy findings.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We compiled a continuous cohort of deceased donor kidneys transplanted at our institution from 1/1/2006 to 12/31/2016 that had at least one procurement biopsy performed, and excluded cases with missing biopsy reports and those used in multiorgan transplants. Suboptimal histology was defined as the presence of advanced sclerosis in greater than or equal to one biopsy compartment (glomeruli, tubules/interstitium, vessels). We calculated κ coefficients to assess agreement in optimal versus suboptimal classification between sequential biopsy reports for kidneys that underwent multiple procurement biopsies and used time-to-event analysis to evaluate the association between first versus second biopsies and patient and allograft survival.

RESULTS

Of the 1011 kidneys included in our cohort, 606 (60%) had multiple procurement biopsies; 98% had first biopsy performed at another organ procurement organization and their second biopsy performed locally. Categorical agreement was highest for vascular disease (κ=0.17) followed by interstitial fibrosis and tubular atrophy (κ=0.12) and glomerulosclerosis (κ=0.12). Overall histologic agreement (optimal versus suboptimal) was κ=0.15. First biopsy histology had no association with allograft survival in unadjusted or adjusted analyses. However, second biopsy optimal histology was associated with a higher probability of death-censored allograft survival, even after adjusting for donor and recipient factors (adjusted hazard ratio, 0.50; 95% confidence interval, 0.34 to 0.75; P=0.001).

CONCLUSIONS

Deceased donor kidneys that underwent multiple procurement biopsies often displayed substantial differences in histologic categorization in sequential biopsies, and there was no association between first biopsy findings and post-transplant outcomes.

Quantifying Donor Effects on Transplant Outcomes Using Kidney Pairs from Deceased Donors

BACKGROUND AND OBJECTIVES

In kidney transplantation, the relative contribution of donor versus other factors on clinical outcomes is unknown. We sought to quantify overall donor effects on transplant outcomes for kidney donations from deceased donors.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

For paired donations from deceased donors resulting in transplants to different recipients, the magnitude of donor effects can be quantified by examining the excess of concordant outcomes within kidney pairs beyond chance concordance. Using data from the Organ Procurement and Transplantation Network between the years 2013 and 2017, we examined concordance measures for delayed graft function, death-censored 1-year graft failure, and death-censored 3-year graft failure. The concordance measures were excess relative risk, excess absolute risk, and the fixation index (where zero is no concordance and one is perfect concordance). We further examined concordance in strata of kidneys with similar values of the Kidney Donor Profile Index, a common metric of organ quality.

RESULTS

If the transplant of the kidney mate resulted in delayed graft function, risk for delayed graft function was 19% higher (95% confidence interval [95% CI], 18% to 20%), or 1.76-fold higher (95% CI, 1.73- to 1.80-fold), than baseline. If a kidney graft failed within 1 year, then the kidney mate's risk of failure was 6% higher (95% CI, 4% to 9%), or 2.85-fold higher (95% CI, 2.25- to 3.48-fold), than baseline. For 3-year graft failure, the excess absolute risk was 7% (95% CI, 4% to 10%) but excess relative risk was smaller, 1.91-fold (95% CI, 1.56- to 2.28-fold). Fixation indices were 0.25 for delayed graft function (95% CI, 0.24 to 0.27), 0.07 for 1-year graft failure (95% CI, 0.04 to 0.09), and 0.07 for 3-year graft failure (95% CI, 0.04 to 0.10). Results were similar in strata of kidneys with a similar Kidney Donor Profile Index.

CONCLUSIONS

Overall results indicated that the donor constitution has small or moderate effect on post-transplant clinical outcomes.

Functional status-based risk-benefit analyses of high-KDPI kidney transplant versus dialysis

Yearly, over half of deceased-donor kidneys with kidney donor profile index (KDPI) > 85 were discarded, yet they could improve survival outcomes for dialysis patients. The potential risk of high-KDPI kidney transplant (KT) depends on the patient's overall health summarized by functional status, which should be examined. The analyzed cohort consisted of adult deceased-donor KT candidates on dialysis listed in 2005-2014. A multivariate Cox proportional hazards model was fitted with functional status, measured using Karnofsky Performance Score (KPS), and transplant status as time-varying covariates. Derived from the Cox model, survival curves were analyzed to compare the survival outcomes between dialysis and transplant with different kidney qualities across three different KPS strata: 10-40, 50-70, and 80-100. With KDPI 0-99 KT, KPS 10-40 patients will survive ≥4.38 years median compared with 3.21 years median if they remained on dialysis. For KPS 50+ patients, the median survival years increase from 5.82 to 6.60 years on dialysis to ≥7.83 years after KDPI < 100 KT. The risk-adjusted analyses suggested that patients are expected to benefit more from KDPI 81-99 KT than from remaining on dialysis.

Examining the Increased Rates of Deceased Donor Kidney Nonutilization in Australia: What Has Changed?

BACKGROUND

From 2013, Australia has experienced a sustained increase in the proportion of deceased donor kidneys that are retrieved but not utilized for transplantation. We aimed to determine whether this could be explained by changes in donor characteristics over time.

METHODS

Registry data were used to examine predictors of kidney nonutilization over the period 2005-2017. Multilevel mixed effect logistic regression modeling and propensity score analysis were used to determine whether era of donation (2013-2017 versus 2005-2012) was an independent predictor of organ nonutilization after controlling for donor characteristics.

RESULTS

A total of 7810 kidneys were retrieved for the purpose of transplantation with 334 (4.3%) not utilized. The nonutilization rate was 5.8% in 2013-2017 compared to 2.7% in 2005-2012. Despite adjustment for donor characteristics, donation in the more recent era remained a significant predictor of kidney nonutilization (adjusted odds ratio, 1.98; 95% confidence interval, 1.54-2.54; P < 0.001). This finding was confirmed in the propensity score analysis.

CONCLUSIONS

Kidneys retrieved in Australia since 2013 were more likely not to be utilized for transplantation even after adjusting for changes in donor characteristics. The abrupt increase may be explained by increased clinical risk aversion, changes in unmeasured donor factors or logistical issues. Although nonutilization rates in Australia remain low by international standards, further clinical auditing of the reasons for offer decline may help to optimize resource utilization and maximize transplant opportunities.

National Variation in Increased Infectious Risk Kidney Offer Acceptance

BACKGROUND

Despite providing survival benefit, increased risk for infectious disease (IRD) kidney offers are declined at 1.5 times the rate of non-IRD kidneys. Elucidating sources of variation in IRD kidney offer acceptance may highlight opportunities to expand use of these life-saving organs.

METHODS

To explore center-level variation in offer acceptance, we studied 6765 transplanted IRD kidneys offered to 187 transplant centers between 2009 and 2017 using Scientific Registry of Transplant Recipients data. We used multilevel logistic regression to determine characteristics associated with offer acceptance and to calculate the median odds ratio (MOR) of acceptance (higher MOR indicates greater heterogeneity).

RESULTS

Higher quality kidneys (per 10 units kidney donor profile index; adjusted odds ratio [aOR], 0.94; 95% confidence interval [CI], 0.92-0.95), higher yearly volume (per 10 deceased donor kidney transplants; aOR, 1.08, 95% CI, 1.06-1.10), smaller waitlist size (per 100 candidates; aOR, 0.97; 95% CI, 0.95-0.98), and fewer transplant centers in the donor service area (per center; aOR, 0.88; 95% CI, 0.85-0.91) were associated with greater odds of IRD acceptance. Adjusting for donor and center characteristics, we found wide heterogeneity in IRD offer acceptance (MOR, 1.96). In other words, if listed at a center with more aggressive acceptance practices, a candidate could be 2 times more likely to have an IRD kidney offer accepted.

CONCLUSIONS

Wide national variation in IRD kidney offer acceptance limits access to life-saving kidneys for many transplant candidates.

Variation in use of procurement biopsies and its implications for discard of deceased donor kidneys recovered for transplantation

The use of procurement biopsies in deceased donor kidney acceptance is controversial. We analyzed Scientific Registry of Transplant Recipients data (n = 59 328 allografts, 2014-2018) to describe biopsy practices across US organ procurement organizations (OPOs) and examine relationships with discards, using hierarchical modeling to account for OPO and donor factors. Median odds ratios (MORs) provide the median of the odds that allografts with identical reported traits would be biopsied or discarded from 2 randomly drawn OPOs. Biopsies were obtained for 52.7% of kidneys. Biopsy use rose in a graded manner with kidney donor profile index (KDPI). Biopsy rates differed significantly among OPOs (22.8% to 77.5%), even after adjustment for KDPI and other donor factors. Discard rates also varied from 6.6% to 32.1% across OPOs. After adjustment for donor factors and OPO, biopsy was associated with more than 3 times the likelihood of discard (adjusted odds ratio [_95%LCL aOR_95%UCL ], _3.29 3.51_3.76 ). This association was most pronounced for low-risk (KDPI <20) kidneys (aOR, _5.45 6.47_7.69 ), with minimal impact at KDPI >85 (aOR, _0.88 1.15_1.51 ). Adjusted MORs for kidney discard and biopsy were greatest for low-risk kidneys. Reducing the rate of unnecessary biopsy and improving the accuracy of histologic assessments in higher KDPI organs may help reduce graft discard rates.

Leveraging marginal structural modeling with Cox regression to assess the survival benefit of accepting vs declining kidney allograft offers

Existing studies evaluating the survival benefit of kidney transplantation were unable to incorporate time-updated information on decisions related to each organ offer. We used national registry data, including organ turndown data, to evaluate the survival benefit of accepting vs turning down kidney offers in candidates waitlisted from 2007-2013. Among candidates who declined their first offer, only 43% ultimately received organ transplantations. Recipients who later underwent organ transplantation after declining their first offer had markedly longer wait times than recipients who accepted their first offer, and 56% received kidney transplants that were of similar or lower quality compared to their initial offer. In marginal structural modeling analyses accounting for time-updated offer characteristics (including Kidney Donor Profile Index, Public Health System risk status, and pumping), after 3 months posttransplant, there was a significant survival benefit of accepting an offer (adjusted hazard ratio 0.76, 95% confidence interval 0.66-0.89) that was similar among diabetics, candidates aged >65 years, and candidates living in donor service areas with the longest waitlist times. After carefully accounting for the effect of donor quality, we confirm that the survival benefit of accepting an organ offer is clinically meaningful and persistent beyond 3 months post-kidney transplantation, including high-risk subgroups of organ transplantation candidates.

Changes in Utilization and Discard of HCV Antibody-Positive Deceased Donor Kidneys in the Era of Direct-Acting Antiviral Therapy

BACKGROUND

The availability of direct-acting antiviral (DAA) therapy might have impacted use of hepatitis C virus (HCV)-infected (HCV+) deceased donor kidneys for transplantation.

METHODS

We used 2005 to 2018 Scientific Registry of Transplant Recipients data to identify 18 936 candidates willing to accept HCV+ kidneys and 3348 HCV+ recipients of HCV+ kidneys. We compared willingness to accept, utilization, discard, and posttransplant outcomes associated with HCV+ kidneys between 2 treatment eras (interferon [IFN] era, January 1, 2005 to December 5, 2013 vs DAA era, December 6, 2013 to August 2, 2018). Models were adjusted for candidate, recipient, and donor factors where appropriate.

RESULTS

In the DAA era, candidates were 2.2 times more likely to list as willing to accept HCV+ kidneys (adjusted odds ratio, 2.072.232.41; P < 0.001), and HCV+ recipients were 1.95 times more likely to have received an HCV+ kidney (adjusted odds ratio, 1.761.952.16; P < 0.001). Median Kidney Donor Profile Index of HCV+ kidneys decreased from 77 (interquartile range [IQR], 59-90) in 2005 to 53 (IQR, 40-67) in 2017. Kidney Donor Profile Index of HCV- kidneys remained unchanged from 45 (IQR, 21-74) to 47 (IQR, 24-73). After adjustment, HCV+ kidneys were 3.7 times more likely to be discarded than HCV- kidneys in the DAA era (adjusted relative rate, 3.363.674.02; P < 0.001); an increase from the IFN era (adjusted relative rate, 2.783.023.27; P < 0.001). HCV+ kidney use was concentrated within a subset of centers; 22.5% of centers performed 75% of all HCV+ kidney transplants in the DAA era. Mortality risk associated with HCV+ kidneys remained unchanged (aHR, 1.071.191.32 in both eras).

CONCLUSIONS

Given the elevated risk of death on dialysis facing HCV+ candidates, improving quality of HCV+ kidneys, and DAA availability, broader utilization of HCV+ kidneys is warranted to improve access in this era of organ shortage.

Prospective Validation of Prediction Model for Kidney Discard

BACKGROUND

Many kidneys are discarded every year, with 3631 kidneys discarded in 2016 alone. Identifying kidneys at high risk of discard could facilitate "rescue" allocation to centers more likely to transplant them. The Probability of Delay or Discard (PODD) model was developed to identify marginal kidneys at risk of discard or delayed allocation beyond 36 hours of cold ischemia time. However, PODD has not been prospectively validated, and patterns of discard may have changed after policy changes such as the introduction of Kidney Donor Profile Index and implementation of the Kidney Allocation System (KAS).

METHODS

We prospectively validated the PODD model using Scientific Registry of Transplant Recipients data in the KAS era (January 1, 2015, to March 1, 2018). C statistic was calculated to assess accuracy in predicting kidney discard. We assessed clustering in centers' utilization of kidneys with PODD >0.6 ("high-PODD") using Gini coefficients. Using match run data from January 1, 2015, to December 31, 2016, we examined distribution of these high-PODD kidneys offered to centers that never accepted a high-PODD kidney.

RESULTS

The PODD model predicted discard accurately under KAS (C-statistic, 0.87). Compared with utilization of low-PODD kidneys (Gini coefficient = 0.41), utilization of high-PODD kidneys was clustered more tightly among a few centers (Gini coefficient, 0.84 with >60% of centers never transplanted a high-PODD kidneys). In total, 11684 offers (35.0% of all high-PODD offers) were made to centers that never accepted a high-PODD kidney.

CONCLUSIONS

Prioritizing allocation of high-PODD kidneys to centers that are more likely to transplant them might help reduce kidney discard.