Progress in Pathological Diagnosis after Kidney Transplantation: Current Trend and Future Perspective

Advances in immunosuppressive therapy; posttransplant management of allograft rejection; and measures against infectious diseases, cardiovascular diseases, and malignancy dramatically improved graft and patient survival after kidney transplantation (KT). Among them, kidney allograft biopsy is an important tool and the gold standard for the diagnosis of various kidney allograft injuries, including allograft rejection, virus-induced nephropathy, calcineurin inhibitor toxicity, and posttransplant glomerular diseases. The Banff Conference on Allograft Pathology has contributed to establishing the diagnostic criteria for kidney allograft rejection and polyomavirus-associated nephropathy that are used as a common standard worldwide. In addition to the for-cause biopsy, many transplant centers perform protocol biopsies in the early and late posttransplant periods to detect and treat allograft injury earlier. Preimplantation biopsy in deceased-donor KT has also been performed, especially in the marginal donor, and attempts have been made to predict the prognosis in combination with clinical information and the renal resistance of hypothermic machine perfusion. Regarding the preimplantation biopsy from a living kidney donor, it can provide useful information on aging and/or early changes in lifestyle diseases, such as glomerulosclerosis, tubulointerstitial changes, and arterial and arteriolar sclerosis, and be used as a reference for the subsequent management of living donors. In this review, morphologic features of important kidney allograft pathology, such as allograft rejection and polyomavirus-associated nephropathy, according to the latest Banff classification and additional information derived from protocol biopsy, and future perspectives with recently developed technologies are discussed.

Kidney Transplantation Outcome Predictions (KTOP): A Risk Prediction Tool for Kidney Transplants from Brain-dead Deceased Donors Based on a Large European Cohort

BACKGROUND

European kidney donation shortages mandate efficient organ allocation by optimizing the prediction of success for individual recipients.

OBJECTIVE

To develop the first European online risk tool for kidney transplant outcomes on the basis of recipient-only and recipient plus donor characteristics.

DESIGN, SETTING, AND PARTICIPANTS

We used individual recipient and donor risk factors and three outcomes (death, death with functioning graft [DWFG], and graft loss) for 32 958 transplants within the Eurotransplant kidney allocation system and the Eurotransplant senior program between January 2006 and May 2018 in eight European countries to develop and validate a risk tool.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Cox proportional-hazards models were used to analyze the association of risk factors with overall patient mortality, and proportional subdistribution hazard regression models for their association with graft loss and DWFG. Prediction models were developed with recipient-only and recipient-donor risk factors. Sensitivity analyses based on time-specific area under the receiver operating characteristic curve (AUC) with leave-one-country-out validation were performed and calibration plots were generated.

RESULTS AND LIMITATIONS

The 10-yr cumulative incidence rate was 37% for mortality, 12% for DWFG, and 41% for graft loss. In recipient-donor models the leading risk factors for mortality were recipient diabetes (hazard ratio [HR] 10.73), retransplantation (HR 3.08 per transplant), and recipient age (HR 1.08). Effects were similar for DWFG. For graft loss, diabetes (subdistributional HR [SHR] 1.32), increased donor age (SHR 1.02), and prolonged cold ischemia time (SHR 1.02) had increased SHRs. All p values were <0.001.

CONCLUSIONS

Previously identified risk factors for outcomes following kidney transplants allow for outcome prediction with 10-yr AUC values of up to 0.81.

PATIENT SUMMARY

Using European data, we estimated individual risks to predict the success of kidney transplants and support physicians in decision-making. An online tool is now available (https://riskcalc.org/ktop/) for predicting kidney transplant outcomes both before and after a donor has been identified.

Donor characteristics and their impact on kidney transplantation outcomes: Results from two nationwide instrumental variable analyses based on outcomes of donor kidney pairs accepted for transplantation

BACKGROUND

Donor-characteristics and donor characteristics-based decision algorithms are being progressively used in the decision process whether or not to accept an available donor kidney graft for transplantation. While this may improve outcomes, the performance characteristics of the algorithms remains moderate. To estimate the impact of donor factors of grafts accepted for transplantation on transplant outcomes, and to test whether implementation of donor-characteristics-based algorithms in clinical decision-making is justified, we applied an instrumental variable analysis to outcomes for kidney donor pairs transplanted in different individuals.

METHODS

This analysis used (dis)congruent outcomes of kidney donor pairs as an instrument and was based on national transplantation registry data for all donor kidney pairs transplanted in separate individuals in the Netherlands (1990-2018, 2,845 donor pairs), and the United Kingdom (UK, 2000-2018, 11,450 pairs). Incident early graft loss (EGL) was used as the primary discriminatory factor. It was reasoned that a scenario with a dominant impact of donor variables on transplantation outcomes would result in high concordance of EGL in both recipients, whilst dominance of asymmetrical outcomes could indicate a more complex scenario, involving an interaction of donor, procedural and recipient factors.

FINDINGS

Incidences of congruent EGL (Netherlands: 1·2%, UK: 0·7%) were slightly lower than the arithmetical (stochastic) incidences, suggesting that once a graft has been accepted for transplantation, donor factors minimally contribute to incident EGL. A long-term impact of donor factors was explored by comparing outcomes for functional grafts from donor pairs with asymmetrical vs. symmetrical outcomes. Recipient survival was similar for both groups, but a slightly compromised graft survival was observed for grafts with asymmetrical outcomes in the UK cohort: (10-years Hazard Ratio for graft loss: 1·18 [1·03-1·35] p<0·018); and 5 years eGFR (48·6 [48·3-49·0] vs. 46·0 [44·5-47·6] ml/min in the symmetrical outcome group, p<0·001).

INTERPRETATION

Our results suggest that donor factors for kidney grafts deemed acceptable for transplantation impact minimally on transplantation outcomes. A strong reliance on donor factors and/or donor-characteristics-based decision algorithms could result in unjustified rejection of grafts. Future efforts to optimize transplant outcomes should focus on a better understanding of the recipient factors underlying transplant outcomes.

FUNDING

None.

Evaluation of Expanded Criteria Donors Using the Kidney Donor Profile Index and the Preimplantation Renal Biopsy

The increasing comorbidity of kidney transplant (KT) donors make it necessary to develop scores to correctly assess the quality of kidney grafts. This study analyzes the usefulness of the preimplantation biopsy and the Kidney Donor Profile Index (KDPI) as indicators of KT survival from expanded criteria donors (ECD). Retrospective study of KT in our center between January 2010 to June 2019 who received a kidney from an ECD and underwent a preimplantation biopsy. 266 KT were included. Graft survival was categorized by KDPI quartiles: Q1 = 86%, Q2 = 95%, Q3 = 99% and Q4 = 100%. KT from KDPI Q1 presented better survival (p = 0.003) and Q4 donors had worse renal function (p = 0.018) and poorer glomerular filtration rate (3rd month; p = 0.017, 1st year; p = 0.010). KT survival was analyzed according to KDPI quartile and preimplantation biopsy score simultaneously: Q1 donors with biopsy score ≤3 had the best survival, especially comparing against Q3 with a biopsy score >3 and Q4 donors (p = 0.014). In multivariable analysis, hyaline arteriopathy, glomerulosclerosis, and KDPI Q4 were predictors for graft survival. High KDPI and a greater histological injury in the preimplantation biopsy, especially glomerular and vascular lesions, were related to a higher rate of KT loss from ECD.

Molecular Markers of Kidney Transplantation Outcome: Current Omics Tools and Future Developments

Purpose of review: The emerging field of molecular predictive medicine is aiming to change the traditional medical approach in renal transplantation. Many studies have explored potential biomarker molecules with predictive properties in renal transplantation, issued from omics research. Herein, we review the biomarker molecules of four technologies (i.e., Genomics, Transcriptomics, Proteomics, and Metabolomics) associated with favorable kidney transplant outcomes. Recent findings: Several panels of molecules have been associated with the outcome that the majority of markers are related to inflammation and immune response; although. other molecular ontologies are also represented, such as proteasome, growth, regeneration, and drug metabolism. Throughout this review, we highlight the lack of properly validated statistical demonstration. Indeed, the most preeminent molecular panels either remain at the limited size study stage or are not confirmed during large-scale studies. At the core of this problem, we identify the methodological shortcomings and propose a comprehensive workflow for discovery and validation of molecular biomarkers that aims to improve the relevance of these tools in the future. Summary: Overall, adopting a patient management through omics approach could bring remarkable improvement to transplantation success. An increased effort and investment between scientists, medical biologists, and clinicians seem to be the path toward a proper solution.

Organ allocation in pediatric abdominal transplant

Pediatric patients constitute an important group within the general transplant population, given the opportunity to significantly extend their lives with successful transplantation. Children have historically received special consideration under the various abdominal solid organ allocation algorithms, but matching patients with size and weight restrictions with appropriate donors remains an ongoing issue. Here, we describe the historical trends in pediatric organ allocation policies for liver, kidney, intestine, and pancreas transplantation. We also review recent changes to these allocation policies, with particular attention to recent amendments to geographical prioritization, with the dissolution of donor service areas and United Network for Organ Sharing (UNOS) regions and the subsequent creation of acuity circles.

The Kidney Donor Profile Index (KDPI) Correlates With Histopathologic Findings in Post-reperfusion Baseline Biopsies and Predicts Kidney Transplant Outcome

Background

The increasing organ shortage in kidney transplantation leads to the necessity to use kidneys previously considered unsuitable for transplantation. Numerous studies illustrate the need for a better decision guidance rather than only the classification into kidneys from standard or expanded criteria donors referred to as SCD/ECD-classification. The kidney donor profile index (KDPI) exhibits a score utilizing a much higher number of donor characteristics. Moreover, graft biopsies provide an opportunity to assess organ quality.

Methods

In a single center analysis 383 kidney transplantations (277 after deceased and 106 after living donation) performed between January 1st, 2006, and December 31st, 2016, retrospectively underwent SCD/ECD and KDPI scoring. Thereby, the quality of deceased donor kidneys was assessed by using the KDPI and the living donor kidneys by using the living KDPI, in the further analysis merged as (L)KDPI. Baseline biopsies taken 10 min after the onset of reperfusion were reviewed for chronic and acute lesions. Survival analyses were performed using Kaplan-Meier analysis and Cox proportional hazards analysis within a 5-year follow-up.

Results

The (L)KDPI correlated with glomerulosclerosis (r = 0.30, p < 0.001), arteriosclerosis (r = 0.33, p < 0.001), interstitial fibrosis, and tubular atrophy (r = 0.28, p < 0.001) as well as the extent of acute tubular injury (r = 0.20, p < 0.001). The C-statistic of the (L)KDPI concerning 5-year death censored graft survival was 0.692. Around 48% of ECD-kidneys were classified as (L)KDPI<85%. In a multivariate Cox proportional hazard analysis including (preformed) panel reactive antibodies, cold ischemia time, (L)KDPI, and SCD/ECD-classification, the (L)KDPI was significantly associated with risk of graft loss (hazard ratio per 10% increase in (L)KDPI: 1.185, 95% confidence interval: 1.033–1.360, p = 0.025). Survival analysis revealed decreased death censored (p < 0.001) and non-death censored (p < 0.001) graft survival in kidneys with an increasing (L)KDPI divided into groups of <35, 35–85, and >85%, respectively.

Conclusion

With a higher granularity compared to the SCD/ECD-classification the (L)KDPI is a promising tool to judge graft quality. The correlation with chronic and acute histological lesions in post-reperfusion kidney biopsies underlines the descriptive value of the (L)KDPI. However, its prognostic value is limited and underlines the urgent need for a more precise prognostic tool adopted to European kidney transplant conditions.

Disparate Formulations for Machine Perfusion: A Survey of Organ Procurement Organizations' Medication Additives and Outcome Analyses

OBJECTIVES

Machine perfusionfor kidney preservation is a common practice. There is no consensus on the best formula for perfusion solutions. We aimed to discern the additives that organ procurement organizations in the United States include in their perfusate and the impact of these additives on transplant outcomes.

MATERIALS AND METHODS

A telephone survey of all 58 organ procurement organizations in the United States regarding additives to their perfusion solutions was conducted. The survey data were merged with transplant recipient outcome data from the United Network for Organ Sharing database.The final analysis included perfused kidneys between January 2014 and March 2019. Logistic regressions were performed to investigate whether a particular perfusion formula was associated with delayed graft function, primary nonfunction, or early graft failure.

RESULTS

Additives correlated with decreased rates of graft failure were mannitol in all kidneys and kidneys of lower quality (P < .01) and penicillin/ampicillin in all kidneys (P < .05). Additives associated with increased graft failure regardless of type included verapamil in all kidneys (P < .05) and kidneys of lower quality (P < .01) and arginine with glutathione in all kidneys and low-quality kidneys alone (P < .01).

CONCLUSIONS

Further outcomes research and standardized guidelines for additives in machine perfusion of kidneys across all organ procurement organizations are needed.

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.

Machine learning support for decision making in kidney transplantation: step-by-step development of a technological solution (Preprint)

Background

Kidney transplantation is the preferred treatment option for patients with end-stage renal disease. To maximize patient and graft survival, the allocation of donor organs to potential recipients requires careful consideration.

Objective

This study aimed to develop an innovative technological solution to enable better prediction of kidney transplant survival for each potential donor-recipient pair.

Methods

We used deidentified data on past organ donors, recipients, and transplant outcomes in the United States from the Scientific Registry of Transplant Recipients. To predict transplant outcomes for potential donor-recipient pairs, we used several survival analysis models, including regression analysis (Cox proportional hazards), random survival forests, and several artificial neural networks (DeepSurv, DeepHit, and recurrent neural network [RNN]). We evaluated the performance of each model in terms of its ability to predict the probability of graft survival after kidney transplantation from deceased donors. Three metrics were used: the C-index, integrated Brier score, and integrated calibration index, along with calibration plots.

Results

On the basis of the C-index metrics, the neural network–based models (DeepSurv, DeepHit, and RNN) had better discriminative ability than the Cox model and random survival forest model (0.650, 0.661, and 0.659 vs 0.646 and 0.644, respectively). The proposed RNN model offered a compromise between the good discriminative ability and calibration and was implemented in a technological solution of technology readiness level 4.

Conclusions

Our technological solution based on the RNN model can effectively predict kidney transplant survival and provide support for medical professionals and candidate recipients in determining the most optimal donor-recipient pair.

Body Mass Index and Kidney Donor Profile Index as Prognostic Markers of the Outcome of Renal Transplantation

BACKGROUND

The aim of this study was to determine the effects of Kidney Donor Profile Index (KDPI) and body mass index (BMI) of the deceased donor on the kidney allograft outcome 1 year after transplantation.

METHODS

We retrospectively studied 98 deceased kidney allograft donors with a mean age of 56 ± 12 years. The donors were divided into 5 groups according to their BMI: Normal ΒΜΙ = 25 (n = 25); ΒΜΙ 25 to 29 = Overweight (n = 33); ΒΜΙ 30 to 34.9 = Obese class I (n = 19); ΒΜΙ 35 to 39 = Obese class ΙΙ (n = 11); and ΒΜΙ >40 = Obese class III (n = 10). We examined the impact of the deceased donor's BMI and KDPI on delayed graft function (DGF) and estimated renal glomerular filtration rate (eGFR) (measured by the Chronic Kidney Disease Epidemiology Collaboration equation) 1 year after transplantation.

RESULTS

Donor BMI significantly increased the prevalence of DGF (P = .031), and it was associated with higher cold ischemia time (P = .021). However, there was no significant association between the aforementioned BMI groups and 1-year eGFR (P = 0.57), as deceased grafts from donors with increased BMI (BMI > 40) gained sufficient renal function during the first year of transplantation. Moreover, high KDPI was associated not only with DGF (P = .015), but also with decreased values of eGFR (P = .033).

CONCLUSION

In this population, we identified no significant association between donor BMI and long-term clinical outcomes in deceased donor kidney transplants. KDPI, and not ΒΜΙ, of the deceased donor seems to be a good prognostic factor of renal function at the end of the first year after kidney transplant, whereas high BMI and high KDPI markedly induce DGF.

Impaired renal function before kidney procurement has a deleterious impact on allograft survival in very old deceased kidney donors

As the use of elderly kidney donors for transplantation is increasing with time, there is a need to understand which factors impact on their prognosis. No data exist on the impact of an impaired renal function (IRF) in such population. 116 kidney recipients from deceased kidney donors over 70 years were included from 2005 to 2015 in a single-center retrospective study. IRF before organ procurement was defined as a serum creatinine above 1.0 mg/dl or a transient episode of oligo-anuria. Mean ages for donors and recipients were respectively 74.8 ± 3.5 and 66.7 ± 8.0. Graft survival censored for death at 5 years was of 77%. Using a multivariate analysis by Cox model, the only predictor of graft loss present in the donor was IRF before organ procurement (HR 4.2 CI95[1.8–9.7]). IRF was also associated with significant lower estimated glomerular filtration rates up to 1 year post-transplantation. By contrast, KDPI score (median of 98 [96–100]), was not associated with the risk of graft failure. Then, IRF before kidney procurement may define a risk subgroup among very-old deceased kidney donors, in whom pre-implantatory biopsies, dual kidney transplantation or calcineurin inhibitor-free immunosuppressive regimen could help to improve outcomes.

Time-to-event analysis in economic evaluations: a comparison of modelling methods to assess the cost-effectiveness of transplanting a marginal quality kidney

BACKGROUND

Economic-evaluations using decision analytic models such as Markov-models (MM), and discrete-event-simulations (DES) are high value adds in allocating resources. The choice of modelling method is critical because an inappropriate model yields results that could lead to flawed decision making. The aim of this study was to compare cost-effectiveness when MM and DES were used to model results of transplanting a lower-quality kidney versus remaining waitlisted for a kidney.

METHODS

Cost-effectiveness was assessed using MM and DES. We used parametric survival models to estimate the time-dependent transition probabilities of MM and distribution of time-to-event in DES. MMs were simulated in 12 and 6 monthly cycles, out to five and 20-year time horizon.

RESULTS

DES model output had a close fit to the actual data. Irrespective of the modelling method, the cycle length of MM or the time horizon, transplanting a low-quality kidney as compared to remaining waitlisted was the dominant strategy. However, there were discrepancies in costs, effectiveness and net monetary benefit (NMB) among different modelling methods. The incremental NMB of the MM in the 6-months cycle lengths was a closer fit to the incremental NMB of the DES. The gap in the fit of the two cycle lengths to DES output reduced as the time horizon increased.

CONCLUSION

Different modelling methods were unlikely to influence the decision to accept a lower quality kidney transplant or remain waitlisted on dialysis. Both models produced similar results when time-dependant transition probabilities are used, most notable with shorter cycle lengths and longer time-horizons.

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.

Donor-Recipient Matching to Optimize the Utility of High Kidney Donor Profile Index Kidneys

BACKGROUND

In December 2014, the Kidney Donor Profile Index (KDPI) was developed to give more precise information on donor kidney quality. Kidneys with KDPI scores ≥ 85 (K ≥ 85) have been reported to have inferior outcomes to kidneys with KDPI scores < 85.

METHODS

After the implementation of the new Kidney Allocation System, we developed a protocol to evaluate K ≥ 85 use. We analyzed the safety and efficacy of our institutional criteria and evaluated post-transplant outcomes. K ≥ 85 recipients were stratified based on their 1-year creatinine and estimated glomerular filtration rates to elucidate characteristics associated with serum creatinine < 1.7 mg/dL or estimated glomerular filtration rates ≤ 45 mL/min/1.73 m².

RESULTS

From December 2014 to December 2019, 304 deceased donor kidney transplants were performed at Hartford Hospital; 58 (19%) were K ≥ 85 with an average KDPI of 91%. There were 4 graft losses; 2 were death censored. Prolonged cold ischemia time and black recipient race were associated with inferior recipient graft function at 1 year.

CONCLUSIONS

High KDPI kidney use requires a multifaceted evaluation that takes into account donor and recipient characteristics for an ideal match. We have identified several characteristics that may predict optimal post-transplant kidney function.

Donor Kidney Quality and Transplant Outcome: An Economic Evaluation of Contemporary Practice

OBJECTIVES

The study had two main aims. First, we assessed the cost-effectiveness of transplanting deceased donor kidneys of differing quality levels based on the Kidney Donor Profile Index (KDPI). Second, we assessed the cost-effectiveness of remaining on the waiting list until a high-quality kidney becomes available compared to transplanting a lower-quality kidney.

METHODS

A decision analytic model to estimate cost-effectiveness was developed using a Markov process. Separate models were developed for 4 separate KDPI bands, with higher values indicating lower quality. Models were simulated in 1-year cycles for a 20-year time horizon, with transitions through distinct health states relevant to the kidney recipient from the healthcare payer's perspective. Weibull regression was used to calculate the time-dependent transition probabilities in the base analysis. The impact uncertainty arising in model parameters was included by probabilistic sensitivity analysis using the Monte Carlo simulation method. Willingness to pay was considered as Australian $28 000.

RESULTS

Transplanting a kidney of any quality is cost-effective compared to remaining on a waitlist. Transplanting a lower KDPI kidney is cost-effective compared to a higher KDPI kidney. Transplanting lower KDPI kidneys to younger patients and higher KDPI kidneys to older patients is also cost-effective. Depending on dialysis in hopes of receiving a lower KDPI kidney is not a cost-effective strategy for any age group.

CONCLUSION

Efforts should be made by the health systems to reduce the discard rates of low-quality kidneys with the view of increasing the transplant rates.

[Very-old deceased donors in kidney transplantation: How far can we go?]

In order to increase the pool of organ donors, kidney transplantation from very old-donors, notably aged more than 70, is increasing. Compared to the United States, where the use of these grafts does not reach 5%, in France it reaches over 20%. Kidney aging is determined by a progressive glomerusclerosis, interstitial fibrosis, and nephrosclerosis, responsible of a linear decrease of glomerular filtration rate with time. Aging in kidney transplantation goes along also with an increased immunogenicity and risk of ischemia-reperfusion injuries. Hence, the prognosis of these transplantations is worse than those from younger donors, even though it remains better than dialysis. Data is lacking on risk factors of graft loss in this specific population. Hypothermic perfusion machine, pre-implantation kidney biopsy, dual kidney transplantation and immunosuppressive strategies have been evaluated to improve the long-term prognosis of these grafts.

Assessment of Organ Quality in Kidney Transplantation by Molecular Analysis and Why It May Not Have Been Achieved, Yet

Donor organ shortage, growing waiting lists and substantial organ discard rates are key problems in transplantation. The critical importance of organ quality in determining long-term function is becoming increasingly clear. However, organ quality is difficult to predict. The lack of good measures of organ quality is a serious challenge in terms of acceptance and allocation of an organ. The underlying review summarizes currently available methods used to assess donor organ quality such as histopathology, clinical scores and machine perfusion characteristics with special focus on molecular analyses of kidney quality. The majority of studies testing molecular markers of organ quality focused on identifying organs at risk for delayed graft function, yet without prediction of long-term graft outcome. Recently, interest has emerged in looking for molecular markers associated with biological age to predict organ quality. However, molecular gene sets have not entered the clinical routine or impacted discard rates so far. The current review critically discusses the potential reasons why clinically applicable molecular quality assessment using early kidney biopsies might not have been achieved yet. Besides a critical analysis of the inherent limitations of surrogate markers used for organ quality, i.e., delayed graft function, the intrinsic methodological limitations of studies assessing organ quality will be discussed. These comprise the multitude of unpredictable hits as well as lack of markers of nephron mass, functional reserve and regenerative capacity.

Validation of the Living Kidney Donor Profile Index in a European cohort and comparison of long-term outcomes with US results

BACKGROUND

Recently, a risk index for living donor kidney (LDK) transplantation [living kidney donor profile index (LKDPI)] was proposed to compare LDKs with each other and with deceased donor kidneys (DDKs). Until now, the LKDPI has not been validated externally.

METHODS

This long-term retrospective analysis included 1305 consecutive adult kidney transplant recipients who were transplanted 2000-16 in our centre. The Kidney Donor Profile Index (KDPI) was calculated in 889 DDKs and the LKDPI in 416 LDKs. Outcome was followed over a median of 6.5 years.

RESULTS

The median LKDPI was 17 and the median KDPI was 69, with a high proportion of donor kidneys with a very high KDPI (40% KDPI ≥ 80). Categorization of LDK into LKDPI quartiles (LKDPI -45-3, 3-17, 17-33, 33-90) revealed a significant difference in death-censored graft survival. Comparing corresponding subgroups of the LKDPI and KDPI (LKDPI/KDPI 0-20 or 20-40) showed comparable graft survival. A multivariate analysis adjusting for relevant recipient factors revealed the KDPI [hazard ratio (HR) 1.21; P < 0.001) and LKDPI (HR 1.15; P = 0.049) as significant independent predictors of graft loss. Time-to-event receiver operating characteristic analyses for graft survival demonstrated lower predictive discrimination of the LKDPI [area under the curve (AUC) 0.55] compared with the KDPI (AUC 0.66). The 10-year graft survival of LDK recipients was inferior in the USA compared with our centre (79% versus 84%).

CONCLUSIONS

These results provide external validation of the LKDPI to predict death-censored graft survival and confirm comparability of the LKDPI with the KDPI to discriminate post-transplant outcome.

What's the score? A comparison of deceased donor kidney scoring systems and correlation with graft outcome

BACKGROUND

A number of deceased donor kidney scoring systems have been developed to predict post-transplant graft failure. However, studies comparing the predictive ability of these scoring systems to each other are lacking.

METHODS

We used single-center histopathologic and UNOS data from 140 marginal deceased donor kidneys and transplant recipients to compare the predictive accuracy of the Maryland Aggregate Pathology Index (MAPI), Kidney Donor Risk Index (KDRI), Remuzzi, and Nyberg scoring systems for 2-year graft survival using time-dependent receiver operating curves and Kaplan-Meier analysis.

RESULTS

MAPI had the highest predictive accuracy (area under curve [AUC] = 0.81) compared to KDRI (AUC = 0.45), Remuzzi (AUC = 0.59), and Nyberg (AUC = 0.63) for 2-year graft survival. Furthermore, when analyzing each score according to its pre-defined risk strata, MAPI was the only scoring system for which 2-year graft survival was significantly different across strata (84.3% for low risk, 56.5% for intermediate risk, and 50% for high risk, P < .001). Additionally, MAPI was the only risk score significantly associated with 2-year graft survival (hazard ratio per point: 1.12, 95% confidence interval [CI]: 1.01-1.23, P = .03).

CONCLUSIONS

In a single-center cohort of biopsied marginal kidneys used for transplantation, MAPI had the best predictive ability of these four scoring systems. When biopsy data are available for kidneys considered for transplantation, the MAPI score may provide additional information that could be used to better identify kidneys likely to have longer graft survival.

Expanded Criteria Donor Kidneys With Kidney Donor Profile Index ≤ 85%: Are We Doing Enough to Counsel Our Patients?

BACKGROUND

Kidneys at higher risk for allograft failure are defined by the Kidney Donor Profile Index (KDPI) > 85% in the current kidney allocation system (KAS), replacing the historical concept of expanded criteria donor (ECD) kidneys in the previous KAS. Discrepancies exist in the classification of "high-risk kidneys" between the 2 KAS. In the current KAS, only recipients of KDPI > 85% kidneys are counseled about the high risk of allograft failure and are required to sign a consent. In this study, we evaluated the outcomes and allocation of kidneys with discordant classification.

METHODS

Using the Scientific Registry of Transplant Recipients, kidneys transplanted between 01/2002 and 09/2016 were classified according to the old (standard criteria donor [SCD]/ECD) and current (KDPI) KAS. We then grouped them as concordant (KDPI ≤ 85% + SCD or KDPI > 85% + ECD) and discordant (KDPI ≤ 85% + ECD or KDPI > 85% + SCD) kidneys.

RESULTS

Approximately 11% of transplanted kidneys were discordant in classification. Among kidneys with KDPI ≤ 85%, ECD status conferred a 64% (95% CI: 56%-73%) higher risk of allograft failure compared to SCD status. However, SCD/ECD status was not associated with differential outcomes in KDPI > 85% kidneys. These ECD kidneys have KDPIs > 50% and have been transplanted across all estimated post-transplant survival (EPTS) deciles.

CONCLUSION

Adequate counseling about the risk and benefit of accepting ECD kidneys with KDPI ≤ 85% versus waiting on dialysis should be explored with the patients, especially those with lower EPTS.

Time-Effect of Donor and Recipient Characteristics on Graft Survival after Kidney Transplantation

The kidney allocation system (KAS) is based on quality-based "longevity matching" strategies that provide only a momentary snapshot of expected outcomes at the time of transplantation. The purpose of our study was to define on a continuous timeline the relative and mutual interactions of donor and recipient characteristics on graft survival. Total 39,108 subjects who underwent kidney transplant between October 25, 1999 and January 1, 2007 were identified in the United Network for Organ Sharing dataset. Our primary outcome was graft survival. Time-dependent receiver operating characteristic (ROC) curves and area under time-dependent ROC curve (AUC) were used to compare the predictive ability of the two allocation systems. During the first year after transplantation, both donor and recipient models showed identical relevance. From the first to the sixth years, although the two ROC curves were nearly identical, the donor model outweighed the recipient model. Both models intersected again at the sixth year. From that time onward, the ROC curve for recipient characteristics model predominated over the ROC curve for donor characteristics model. The predictive value of the recipient model (AUC = 0.752) was greater than that of the donor model (AUC = 0.673) We hope that this model will provide additional guidance and risk stratification to further optimize organ allocation based on the dynamic interaction of both donor and recipient characteristics over time.

Predicting kidney transplant outcomes with partial knowledge of HLA mismatch

We consider prediction of graft survival when a kidney from a deceased donor is transplanted into a recipient, with a focus on the variation of survival with degree of human leukocyte antigen (HLA) mismatch. Previous studies have used data from the Scientific Registry of Transplant Recipients (SRTR) to predict survival conditional on partial characterization of HLA mismatch. Whereas earlier studies assumed proportional hazards models, we used nonparametric regression methods. These do not make the unrealistic assumption that relative risks are invariant as a function of time since transplant, and hence should be more accurate. To refine the predictions possible with partial knowledge of HLA mismatch, it has been suggested that HaploStats statistics on the frequencies of haplotypes within specified ethnic/national populations be used to impute complete HLA types. We counsel against this, showing that it cannot improve predictions on average and sometimes yields suboptimal transplant decisions. We show that the HaploStats frequency statistics are nevertheless useful when combined appropriately with the SRTR data. Analysis of the ecological inference problem shows that informative bounds on graft survival probabilities conditional on refined HLA typing are achievable by combining SRTR and HaploStats data with immunological knowledge of the relative effects of mismatch at different HLA loci.

Development and validation of a new prediction model for graft function using preoperative marginal factors in living-donor kidney transplantation

BACKGROUND

Recently, living-donor kidney transplantation from marginal donors has been increasing. However, a simple prediction model for graft function including preoperative marginal factors is limited. Here, we developed and validated a new prediction model for graft function using preoperative marginal factors in living-donor kidney transplantation.

METHODS

We retrospectively investigated 343 patients who underwent living-donor kidney transplantation at Kyushu University Hospital (derivation cohort). Low graft function was defined as an estimated glomerular filtration rate of < 45 mL/min/1.73 m² at 1 year. A prediction model was developed using a multivariable logistic regression model, and verified using data from 232 patients who underwent living-donor kidney transplantation at Tokyo Women's Medical University Hospital (validation cohort).

RESULTS

In the derivation cohort, 89 patients (25.9%) had low graft function at 1 year. Donor age, donor-estimated glomerular filtration rate, donor hypertension, and donor/recipient body weight ratio were selected as predictive factors. This model demonstrated modest discrimination (c-statistic = 0.77) and calibration (Hosmer-Lemeshow test, P = 0.83). Furthermore, this model demonstrated good discrimination (c-statistic = 0.76) and calibration (Hosmer-Lemeshow test, P = 0.54) in the validation cohort. Furthermore, donor age, donor-estimated glomerular filtration rate, and donor hypertension were strongly associated with glomerulosclerosis and atherosclerotic vascular changes in the "zero-time" biopsy.

CONCLUSIONS

This model using four pre-operative variables will be a simple, but useful guide to estimate graft function at 1 year after kidney transplantation, especially in marginal donors, in the clinical setting.

Validation of the Kidney Donor Profile Index (KDPI) to assess a deceased donor's kidneys' outcome in a European cohort

The Kidney Donor Profile Index (KDPI) was introduced in the United States in 2014 to guide the decision making of clinicians with respect to accepting or declining a donated kidney. To evaluate whether the KDPI can be applied to a European cohort, we retrospectively assessed 580 adult patients who underwent renal transplantation (brain-dead donors) between January 2007 and December 2014 at our center and compared their KDPIs with their short- and long-term outcomes. This led to the observation of two associations: one between the KDPI and the estimated glomerular filtration rate at one year (1-y-eGFR) and the other between the KDPI and the death-censored allograft survival rate (both p < 0.001). Following this, the individual input factors of the KDPI were analyzed to assess their potential to evaluate the quality of a donor organ. We found that a donor’s age alone is significantly predictive in terms of 1-y-eGFR and death-censored allograft survival (both p < 0.001). Therefore, a donor’s age may serve as a simple reference for future graft function. Furthermore, we found that an organ with a low KDPI or from a young donor has an improved graft survival rate whereas kidneys with a high KDPI or from an older donor yield an inferior performance, but they are still acceptable. Therefore, we would not encourage defining a distinct KDPI cut-off in the decision-making process of accepting or declining a kidney graft.

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.

The impact of kidney donor profile index on delayed graft function and transplant outcomes: A single-center analysis

INTRODUCTION

Renal transplant outcomes result from a combination of factors. Traditionally, donor factors were summarized by classifying kidneys as extended criteria or standard criteria. In 2014, the nomenclature changed to describe donor factors with the kidney donor profile index (KDPI). We aim to evaluate the relationship between KDPI and delayed graft function (DGF), and the impact KDPI on transplant outcomes for both donor after cardiac death (DCD) and donor after brain death (DBD).

METHODS

An IRB-approved single-center retrospective chart review was performed from January 1999 to July 2013. The patients were divided into six groups: DBD KDPI ≤60, DBD KPDI 61-84, DBD KDPI ≥85, DCD KDPI ≤60, DCD KPDI 61-84, and DCD KDPI ≥85. Rates of DGF, patient survival, and graft survival were examined among groups.

RESULTS

A total of 2161 kidney transplants were included. DGF rates increased, and graft and patient survival decreased with increasing KDPI (P < .001). DCD kidneys had higher DGF rates than their DBD counterparts (P < .001). In DCD kidneys, a higher KDPI score did not significantly affect the DGF rates (P > .302). There was no significant difference in graft or patient survival in all-comers when comparing DCD and DBD kidneys with equivalent KDPIs (P > .317). Patients with DGF across all categories demonstrated worse graft half-lives.

CONCLUSION

The KDPI system is an accurate predictor of donor contributions to transplant outcomes. Recipients of DBD kidneys experience an increase in the rate of DGF as their KDPI increases. DCD kidneys have higher DGF rates than their DBD counterparts with similar KDPIs. Patients with documented post-transplant DGF had between 3- and 5-year shorter graft half-lives when compared to recipients that did not experience DGF. Initiatives to reduce the rate of DGF could provide a significant impact on graft survival and result in a reduction in the number of patients requiring retransplant.

Nucleic Acid Tests for BK Polyomavirus Is Critical in Renal Transplant Recipients

This study evaluates the incidence of BK polyomavirus (BKV) and prognosis of BKV infection in kidney transplant recipients (KTRs) who received transplantation in our hospital before and after regular BKV nucleic acid test (NAT) was implemented.

METHODS

The study included 74 KTRs who received a single kidney either from standard- or expanded-criteria deceased donor between March 2011 and March 2017. BKV NATs were regularly checked in 26 patients (group 1) in the first posttransplant year in accordance with current guidelines since NAT was implemented in our laboratory in 2014. We retrospectively compared 48 KTRs (group 2) who either received NAT when necessary in another laboratory or were not checked before 2014.

RESULTS

There was no significant difference in patient characteristics between groups. BKV viruria were confirmed in 8 of 26 (30.8%) group 1 patients, whereas only 2 of 48 (4.2%) BKV infections were confirmed in group 2. None of the BKV(+) KTRs in group 1 developed BK polyomavirus-associated nephropathy (BKVAN), whereas 2 BKV(+) patients (100%) of group 2 developed BKVAN, which indicates renal function deterioration and biopsy-validated nephropathy. There was no significant difference in graft survival and renal function between the 2 groups.

CONCLUSIONS

The risk of BKV infection is considerably higher in KTRs using NAT. Because there is no approval treatment, early diagnosis of BKV infection and early reduction of immunosuppression agents is critical for KTRs. Implementation of regular BKV NAT is mandatory before BKVAN and malignant neoplasms develop.

Are we underestimating the quality of aviremic hepatitis C-positive kidneys? Time to reconsider

Kidney Donor Risk Index (KDRI) introduced in 2009 included hepatitis C serologic but not viremic status of the donors. With nucleic acid amplification testing (NAT) now being mandatory, further evaluation of these donors is possible. We conducted a retrospective matched case-control analysis of adult deceased donor kidney transplants performed between December 5, 2014 to December 31, 2016 with the KDRI score and hepatitis C virus antibody (HCV Ab) and NAT testing status obtained from the United Network for Organ Sharing database. The 205 aviremic HCV Ab+ NAT - kidney transplants were compared to KDRI matched control kidneys that were HCV Ab-NAT-. The aviremic HCV kidneys were recovered from donors who were significantly younger, more likely to be white, and less likely to have hypertension and diabetes. The majority of the recipients of the aviremic HCV kidneys when compared to matched controls were HCV positive: 90.2% vs 4.3%. The recipients were significantly older, were on dialysis for a shorter time, and were transplanted sooner. The graft survival of aviremic HCV kidneys was similar (P < .08). If the HCV status of the aviremic kidneys was assumed to be negative, 122 more kidneys could have been allocated to patients with estimated posttransplant survival <20. Seven kidneys would no longer have Kidney Donor Profile Index >85%. Further policies might consider these findings to appropriately allocate these kidneys.

Association of the kidney allocation system with dialysis exposure before deceased donor kidney transplantation by preemptive wait-listing status

BACKGROUND

It is unknown whether the new kidney transplant allocation system (KAS) has attenuated the advantages of preemptive wait-listing as a strategy to minimize pretransplant dialysis exposure.

METHODS

We performed a retrospective study of adult US deceased donor kidney transplant (DDKT) recipients between December 4, 2011-December 3, 2014 (pre-KAS) and December 4, 2014-December 3, 2017 (post-KAS). We estimated pretransplant dialysis durations by preemptive listing status in the pre- and post-KAS periods using multivariable gamma regression models.

RESULTS

Among 65 385 DDKT recipients, preemptively listed recipients (21%, n = 13 696) were more likely to be white (59% vs 34%, P < 0.001) and have private insurance (64% vs 30%, P < 0.001). In the pre- and post-KAS periods, average adjusted pretransplant dialysis durations for preemptively listed recipients were <2 years in all racial groups. Compared to recipients who were listed after starting dialysis, preemptively listed recipients experienced 3.85 (95% Confidence Interval [CI] 3.71-3.99) and 4.53 (95% CI 4.32-4.74) fewer average years of pretransplant dialysis in the pre- and post-KAS periods, respectively (P < 0.001 for all comparisons).

CONCLUSIONS

Preemptively wait-listed DDKT recipients continue to experience substantially fewer years of pretransplant dialysis than recipients listed after dialysis onset. Efforts are needed to improve both socioeconomic and racial disparities in preemptive wait-listing.

Living donor risk model for predicting kidney allograft and patient survival in an emerging economy

AIM

Living donor kidney is the main source of donor organs in low to middle income countries. We aimed to develop a living donor risk model that predicts graft and patient survival in an emerging economy.

METHODS

We used data from the Sindh Institute of Urology and Transplantation (SIUT) database (n = 2283 recipients and n = 2283 living kidney donors, transplanted between 1993 and 2009) and conducted Cox proportional hazard analyses to develop a composite score that predicts graft and patient survivals.

RESULTS

Donor factors age, creatinine clearance, nephron dose (estimated by donor/recipient body weight ratio) and human leukocyte antigen (HLA) match were included in the living donor risk model. The adjusted hazard ratios (HRs) for graft failures among those who received a kidney with living donor scores (reference to donor score of zero) of 1, 2, 3 and 4 were 1.14 (95%CI: 0.94-1.39), 1.24 (95%CI:1.03-1.49), 1.25 (95%CI:1.03-1.51) and 1.36 (95%CI:1.08-1.72) (P-value for trend =0.05). Similar findings were observed for patient survival.

CONCLUSIONS

Similar to findings in high income countries, our study suggests that donor characteristics such as age, nephron dose, creatinine clearance and HLA match are important factors that determine the long-term patient and graft survival in low income countries. However, other crucial but undefined factors may play a role in determining the overall risk of graft failure and mortality in living kidney donor transplant recipients.

Factors leading to the discard of deceased donor kidneys in the United States

The proportion of deceased donor kidneys procured for transplant but subsequently discarded has been growing steadily in the United States, but factors contributing to the rising discard rate remain unclear. To assess the reasons for and probability of organ discard we assembled a cohort of 212,305 deceased donor kidneys recovered for transplant from 2000-2015 in the SRTR registry that included 36,700 kidneys that were discarded. 'Biopsy Findings' (38.2%) was the most commonly reported reason for discard. The median Kidney Donor Risk Index of discarded kidneys was significantly higher than transplanted organs (1.78 vs 1.12), but a large overlap in the quality of discarded and transplanted kidneys was observed. Kidneys of donors who were older, female, Black, obese, diabetic, hypertensive or HCV-positive experienced a significantly increased odds of discard. Kidneys from donors with multiple unfavorable characteristics were more likely to be discarded, whereas unilaterally discarded kidneys had the most desirable donor characteristics and the recipients of their partner kidneys experienced a one-year death-censored graft survival rate over 90%. There was considerable geographic variation in the odds of discard across the United States, which further supports the notion that factors beyond organ quality contributed to kidney discard. Thus, while the discard of a small fraction of organs procured from donors may be inevitable, the discard of potentially transplantable kidneys needs to be avoided. This will require a better understanding of the factors contributing to organ discard in order to remove the disincentives to utilize less-than-ideal organs for transplantation.

Usefulness of the KDPI in Spain: A comparison with donor age and definition of standard/expanded criteria donor

INTRODUCTION

Kidney donor shortage requires expanding donor selection criteria, as well as use of objective tools to minimize the percentage of discarded organs. Some donor pre-transplant variables such as age, standard/expanded criteria donor (SCD/ECD) definition and calculation of the Kidney Donor Profile Index (KDPI), have demonstrated correlations with patient and graft outcomes. We aimed to establish the accuracy of the three models to determine the prognostic value of kidney transplantation (KT) major outcomes.

MATERIAL AND METHODS

We performed a retrospective study in deceased donor KTs at our institution. Unadjusted Cox and Kaplan-Meier survival, and multivariate Cox analyses were fitted to analyze the impact of donor age, SCD/ECD and KDPI on outcomes.

RESULTS

389 KTs were included. Mean donor age was 53.6±15.2 years; 163 (41.9%) came from ECD; mean KDPI was 69.4±23.4%. Median follow-up was 51.9 months. The unadjusted Cox and Kaplan-Meier showed that the three prognostic variables of interest were related to increased risk of patient death, graft failure and death-censored graft failure. However, in the multivariate analysis only KDPI was related to a higher risk of graft failure (HR 1.03 [95% CI 1.01-1.05]; p=0.014).

CONCLUSIONS

SCD/ECD classification did not provide significant prognostic information about patient and graft outcomes. KDPI was linearly related to a higher risk of graft failure, providing a better assessment. More studies are needed before using KDPI as a tool to discard or accept kidneys for transplantation.

Transplantation of Cold Stored Porcine Kidneys After Controlled Oxygenated Rewarming

The concept of "controlled oxygenated rewarming" (COR) using ex vivo machine perfusion after cold storage was evaluated as tool to improve renal graft function after transplantation. Renal function after 20 min warm ischemia and 21 h cold storage was studied in an auto-transplant model in pigs (25-30 kg, n = 6 per group). In the study group, preimplant ex vivo machine perfusion for 90 min was added after cold storage, including gentle warming up of the graft to 20°C (COR). Kidneys that were only cold stored for 21 h served as controls. In vivo follow up was one week; the remaining native kidney was removed during transplantation. COR significantly improved cortical microcirculation upon early reperfusion and reduced free radical mediated injury and cellular apoptosis. Post-transplant kidney function (peak levels in serum) was also largely and significantly improved in comparison to the control group. A weak inverse correlation was found between renal flow during COR and later peak creatinine after transplantation (r²  = 0.5), better values were seen for oxygen consumption, measured during machine perfusion at 20°C (r²  = 0.81). Gentle graft rewarming prior to transplantation by COR improves post-transplant graft outcome and may also be a valuable adjunct in pretransplant graft assessment.

The kidney allocation system does not appropriately stratify risk of pediatric donor kidneys: Implications for pediatric recipients

Kidney Allocation System (KAS) was enacted in 2014 to improve graft utility, while facilitating transplantation of highly-sensitized patients and preserving pediatric access to high-quality kidneys. Central to this system is the Kidney Donor Profile Index (KDPI), a metric intended to predict transplant outcomes based on donor characteristics but derived using only adult donors. We posited that KAS had inadvertently altered the profile and quantity of kidneys made available to pediatric recipients. This question arose from our observation that most pediatric donors carry a KDPI over 35 and have therefore been rendered relatively inaccessible to pediatric recipients under KAS. Here we explore early trends in pediatric transplantation following KAS, including: (i) use of pediatric donors, (ii) use of Public Health System (PHS) high infectious risk donors, (iii) wait time, and (iv) living donor transplantation. We note some concerning preliminary changes following KAS implementation, including the allocation of fewer deceased donor pediatric kidneys to children and stagnation in pediatric wait times. Moreover, the poor predictive power of the KDPI for adult donors appears to be even worse when applied to pediatric donors. These early trends warrant further observation and consideration of changes in pediatric kidney allocation if they persist.

Normothermic machine perfusion for the assessment and transplantation of declined human kidneys from donation after circulatory death donors

BACKGROUND

A significant proportion of donation after circulatory death (DCD) kidneys are declined for transplantation because of concerns over their quality. Ex vivo normothermic machine perfusion (NMP) provides a unique opportunity to assess the quality of a kidney and determine its suitability for transplantation.

METHODS

In phase 1 of this study, declined human DCD kidneys underwent NMP assessment for 60 min. Kidneys were graded 1-5 using a quality assessment score (QAS) based on macroscopic perfusion, renal blood flow and urine output during NMP. In phase 2 of the study, declined DCD kidneys were assessed by NMP with an intention to transplant them.

RESULTS

In phase 1, 18 of 42 DCD kidneys were declined owing to poor in situ perfusion. After NMP, 28 kidneys had a QAS of 1-3, and were considered suitable for transplantation. In phase 2, ten of 55 declined DCD kidneys underwent assessment by NMP. Eight kidneys had been declined because of poor in situ flushing in the donor and five of these were transplanted successfully. Four of the five kidneys had initial graft function.

CONCLUSION

NMP technology can be used to increase the number of DCD kidney transplants by assessing their quality before transplantation.

Strategies for an Expanded Use of Kidneys From Elderly Donors

The old-for-old allocation policy used for kidney transplantation (KT) has confirmed the survival benefit compared to remaining listed on dialysis. Shortage of standard donors has stimulated the development of strategies aimed to expand acceptance criteria, particularly of kidneys from elderly donors. We have systematically reviewed the literature on those different strategies. In addition to the review of outcomes of expanded criteria donor or advanced age kidneys, we assessed the value of the Kidney Donor Profile Index policy, preimplantation biopsy, dual KT, machine perfusion and special immunosuppressive protocols. Survival and functional outcomes achieved with expanded criteria donor, high Kidney Donor Profile Index or advanced age kidneys are poorer than those with standard ones. Outcomes using advanced age brain-dead or cardiac-dead donor kidneys are similar. Preimplantation biopsies and related scores have been useful to predict function, but their applicability to transplant or refuse a kidney graft has probably been overestimated. Machine perfusion techniques have decreased delayed graft function and could improve graft survival. Investing 2 kidneys in 1 recipient does not make sense when a single KT would be enough, particularly in elderly recipients. Tailored immunosuppression when transplanting an old kidney may be useful, but no formal trials are available.Old donors constitute an enormous source of useful kidneys, but their retrieval in many countries is infrequent. The assumption of limited but precious functional expectancy for an old kidney and substantial reduction of discard rates should be generalized to mitigate these limitations.

Re-evaluating Cut-off Points for the Expansion of Deceased Donor Criteria for Kidney Transplantation in Japan

BACKGROUND

A shortage of donors poses a serious problem for organ transplantation around the world. In response, the concept of the expanded criteria donor (ECD) has been defined to include donors with traditionally less favorable characteristics. That definition has now been accepted and is being applied in kidney transplantation in the United States and Europe. However, the ECD has not yet been defined for deceased donor kidney transplantation in Japan.

PATIENTS AND METHODS

We analyzed data on graft survival and relevant risk factors in patients who received deceased donor kidney transplants through the East Japan Branch of the Japan Organ Transplant network (n = 1051). Recipients were divided into two groups: the standard-function group (estimated glomerular filtration rate [eGFR] ≥20 mL/min/1.73 m²; n = 906) and the poor-function group (eGFR <20 mL/min/1.73 m²; n = 145; Cox proportional hazards regression analysis; P < .0001).

RESULTS

The 10-year survival rate was significantly lower in the poor-function group than in the standard-function group (85.5% vs 22.5%; P < .0001). The two groups differed significantly in recipient and donor risk for graft failure. Recipient risk factors were length of time on dialysis before renal transplantation and incidence of acute rejection after transplantation. Donor risk factors were donor category (heart death), age, history of hypertension, presence of cerebrovascular disease, mean urine output, and donor creatinine level immediately before donor nephrectomy, total ischemic time, and warm ischemic time.

CONCLUSION

Data from deceased donor transplantation should be analyzed in depth to determine which factors influence renal function after transplantation. In addition, ECD standards should be reconsidered for use in a Japanese context.

Raman-based detection of hydroxyethyl starch in kidney allograft biopsies as a potential marker of allograft quality in kidney transplant recipients

In brain-dead donor resuscitation, hydroxyethyl starch (HES) use has been associated with presence of osmotic-nephrosis-like lesions in kidney transplant recipients. Our aim was to determine whether the presence of HES in protocol renal graft biopsies at three months (M3) after transplantation is associated with renal graft quality. According to the HES administered to the donor during the procurement procedure, two groups of patients were defined according graft exposition to HES: HES group, (N = 20) and control group (N = 6). Detection and relative quantification of HES was performed by Raman spectroscopy microimaging on M3 protocol renal graft biopsies. Statistical analyses were used to investigate the association between Raman data and graft characteristics. HES spectral signal was revealed negative in the control group, whereas it was positive in 40% of biopsies from the HES group. In the HES group, a stronger HES signal was associated with a lower risk of graft failure measured by the Kidney Donor Risk Index (KDRI) and was correlated with the allograft kidney function. Thus, HES accumulation in donor kidney, as probed by Raman biophotonic technique, is correlated with the quality of donor kidney and consequently the graft renal function and graft survival.

Changes in Discard Rate After the Introduction of the Kidney Donor Profile Index (KDPI)

Since March 26, 2012, the Kidney Donor Profile Index (KDPI) has been provided with all deceased-donor kidney offers, with the goal of improving the expanded criteria donor (ECD) indicator. Although an improved risk index may facilitate identification and transplantation of marginal yet viable kidneys, a granular percentile system may reduce provider-patient communication flexibility, paradoxically leading to more discards ("labeling effect"). We studied the discard rates of the kidneys recovered for transplantation between March 26, 2010 and March 25, 2012 ("ECD era," N = 28 636) and March 26, 2012 and March 25, 2014 ("KDPI era," N = 29 021) using Scientific Registry of Transplant Recipients (SRTR) data. There was no significant change in discard rate from ECD era (18.1%) to KDPI era (18.3%) among the entire population (adjusted odds ratio [aOR] = 0.97 1.041.10 , p = 0.3), or in any KDPI stratum. However, among kidneys in which ECD and KDPI indicators were discordant, "high risk" standard criteria donor (SCD) kidneys (with KDPI > 85) were at increased risk of discard in the KDPI era (aOR = 1.07 1.421.89 , p = 0.02). Yet, recipients of these kidneys were at much lower risk of death (adjusted Risk Ratio [aRR] = 0.56 0.770.94 at 2 years posttransplant) compared to those remaining on dialysis waiting for low-KDPI kidneys. Our findings suggest that there might be an unexpected, harmful labeling effect of reporting a high KDPI for SCD kidneys, without the expected advantage of providing a more granular risk index.

New Solutions to Reduce Discard of Kidneys Donated for Transplantation

Kidney transplantation is a cost-saving treatment that extends the lives of patients with ESRD. Unfortunately, the kidney transplant waiting list has ballooned to over 100,000 Americans. Across large areas of the United States, many kidney transplant candidates spend over 5 years waiting and often die before undergoing transplantation. However, more than 2500 kidneys (>17% of the total recovered from deceased donors) were discarded in 2013, despite evidence that many of these kidneys would provide a survival benefit to wait-listed patients. Transplant leaders have focused attention on transplant center report cards as a likely cause for this discard problem, although that focus is too narrow. In this review, we examine the risks associated with accepting various categories of donated kidneys, including discarded kidneys, compared with the risk of remaining on dialysis. With the goal of improving access to kidney transplant, we describe feasible proposals to increase acceptance of currently discarded organs.

Organ quality metrics are a poor predictor of costs and resource utilization in deceased donor kidney transplantation

BACKGROUND

The desire to provide cost-effective care has lead to an investigation of the costs of therapy for end-stage renal disease. Organ quality metrics are one way to attempt to stratify kidney transplants, although the ability of these metrics to predict costs and resource use is undetermined.

METHODS

The Scientific Registry of Transplant Recipients database was linked to the University HealthSystem Consortium Database to identify adult deceased donor kidney transplant recipients from 2009 to 2012. Patients were divided into cohorts by kidney criteria (standard vs expanded) or kidney donor profile index (KDPI) score (<85 vs 85+). Length of stay, 30-day readmission, discharge disposition, and delayed graft function were used as indicators of resource use. Cost was defined as reimbursement based on Medicare cost/charge ratios and included the costs of readmission when applicable.

RESULTS

More than 19,500 patients populated the final dataset. Lower-quality kidneys (expanded criteria donor or KDPI 85+) were more likely to be transplanted in older (both P < .001) and diabetic recipients (both P < .001). After multivariable analysis controlling for recipient characteristics, we found that expanded criteria donor transplants were not associated with increased costs compared with standard criteria donor transplants (risk ratio [RR] 0.97, 95% confidence interval [CI] 0.93-1.00, P = .07). KDPI 85+ was associated with slightly lower costs than KDPI <85 transplants (RR 0.95, 95% CI 0.91-0.99, P = .02). When KDPI was considered as a continuous variable, the association was maintained (RR 0.9993, 95% CI 0.999-0.9998, P = .01).

CONCLUSION

Organ quality metrics are less influential predictors of short-term costs than recipient factors. Future studies should focus on recipient characteristics as a way to discern high versus low cost transplantation procedures.