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

Value of original and modified pathological scoring systems for prognostic prediction in paraffin-embedded donor kidney core biopsy

BACKGROUND

No study has validated, compared and adapted scoring systems for prognosis prediction based on donor kidney core biopsy (CB), with less glomeruli than wedge biopsy.

METHODS

A total of 185 donor kidney CB specimens were reviewed using seven scoring systems. The association between the total score, item scores, score-based grading, and allograft prognosis was investigated. In specimens with less than ten glomeruli (88/185, 47.6%), scoring systems were modified by adjusting weights of the item scores.

RESULTS

The Maryland aggregate pathology index (MAPI) score-based grading and periglomerular fibrosis (PGF) associated with delayed graft function (DGF) (Grade: OR = 1.59, p < 0.001; PGF: OR = 1.06, p = 0.006). Total score, score-based grading and chronic lesion score in scoring systems associated with one-year and 3-year eGFR after transplantation. Total-score-based models had similar predictive capacities for eGFR in all scoring systems, except MAPI and Ugarte. Score of glomerulosclerosis (GS), interstitial fibrosis (IF), tubular atrophy (TA), and arteriolar hyalinosis (AH) had good eGFR predictive capacities. In specimens with less than ten glomeruli, modified scoring systems had better eGFR predictive capacities than original scoring systems.

CONCLUSIONS

Scoring systems could predict allograft prognosis in paraffin-embedded CB with ten more glomeruli. A simple and pragmatic scoring system should include GS, IF, TA and AH, with weights assigned based on predictive capacity for prognosis. Replacing GS scores with tubulointerstitial scores could significantly improve the predictive capacity of eGFR. The conclusion should be further validated in frozen section.

Decoding the hallmarks of allograft dysfunction with a comprehensive pan-organ transcriptomic atlas

The pathogenesis of allograft (dys)function has been increasingly studied using 'omics'-based technologies, but the focus on individual organs has created knowledge gaps that neither unify nor distinguish pathological mechanisms across allografts. Here we present a comprehensive study of human pan-organ allograft dysfunction, analyzing 150 datasets with more than 12,000 samples across four commonly transplanted solid organs (heart, lung, liver and kidney, n = 1,160, 1,241, 1,216 and 8,853 samples, respectively) that we leveraged to explore transcriptomic differences among allograft dysfunction (delayed graft function, acute rejection and fibrosis), tolerance and stable graft function. We identified genes that correlated robustly with allograft dysfunction across heart, lung, liver and kidney transplantation. Furthermore, we developed a transfer learning omics prediction framework that, by borrowing information across organs, demonstrated superior classifications compared to models trained on single organs. These findings were validated using a single-center prospective kidney transplant cohort study (a collective 329 samples across two timepoints), providing insights supporting the potential clinical utility of our approach. Our study establishes the capacity for machine learning models to learn across organs and presents a transcriptomic transplant resource that can be employed to develop pan-organ biomarkers of allograft dysfunction.

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.

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.

The Independent Effects of Kidney Length and Vascular Plaque on Ten-Year Outcomes of Extended Criteria Donor Kidney Transplants

The independent effects of deceased donor kidney length and vascular plaque on long-term graft survival are not established. Utilizing DonorNet attachments from 4,480 expanded criteria donors (ECD) recovered between 2008 and 2012 in the United States with at least one kidney biopsied and transplanted, we analyzed the relationship between kidney length and vascular plaques and 10-year hazard of all-cause graft failure (ACGF) using causal inference methods in a Cox regression framework. The composite plaque score (range 0-4) and the presence of any plaque (yes, no) was also analyzed. Kidney length was modeled both categorically (<10, 10-12, >12 cm) as well as numerically, using a restricted cubic spline to capture nonlinearity. Effects of a novel composite plaque score 4 vs. 0 (HR 1.08; 95% CI: 0.96, 1.23) and the presence of any vascular plaque (HR 1.08; 95% CI: 0.98, 1.20) were attenuated after adjustment. Likewise, we identified a potential nonlinear relationship between kidney length and the 10-year hazard of ACGF, however the strength of the relationship was attenuated after adjusting for other donor factors. The independent effects of vascular plaque and kidney length on long-term ECD graft survival were found to be minimal and should not play a significant role in utilization.

European Society for Organ Transplantation (ESOT)-TLJ 3.0 Consensus on Histopathological Analysis of Pre-Implantation Donor Kidney Biopsy: Redefining the Role in the Process of Graft Assessment

The ESOT TLJ 3.0. consensus conference brought together leading experts in transplantation to develop evidence-based guidance on the standardization and clinical utility of pre-implantation kidney biopsy in the assessment of grafts from Expanded Criteria Donors (ECD). Seven themes were selected and underwent in-depth analysis after formulation of PICO (patient/population, intervention, comparison, outcomes) questions. After literature search, the statements for each key question were produced, rated according the GRADE approach [Quality of evidence: High (A), Moderate (B), Low (C); Strength of Recommendation: Strong (1), Weak (2)]. The statements were subsequently presented in-person at the Prague kick-off meeting, discussed and voted. After two rounds of discussion and voting, all 7 statements reached an overall agreement of 100% on the following issues: needle core/wedge/punch technique representatively [B,1], frozen/paraffin embedded section reliability [B,2], experienced/non-experienced on-call renal pathologist reproducibility/accuracy of the histological report [A,1], glomerulosclerosis/other parameters reproducibility [C,2], digital pathology/light microscopy in the measurement of histological variables [A,1], special stainings/Haematoxylin and Eosin alone comparison [A,1], glomerulosclerosis reliability versus other histological parameters to predict the graft survival, graft function, primary non-function [B,1]. This methodology has allowed to reach a full consensus among European experts on important technical topics regarding pre-implantation biopsy in the ECD graft assessment.

Beyond donation to organ utilization in the USA

PURPOSE OF REVIEW

The deceased donor organ pool has broadened beyond young, otherwise healthy head trauma victims. But an abundance of donated organs only benefits patients if they are accepted, expeditiously transported and actually transplanted. This review focuses on postdonation challenges and opportunities to increase the number of transplants through improved organ utilization.

RECENT FINDINGS

We build upon recently proposed changes in terminology for measuring organ utilization. Among organs recovered for transplant, the nonuse rate (NUR REC ) has risen above 25% for kidneys and pancreata. Among donors, the nonuse rate (NUR DON ) has risen to 40% for livers and exceeds 70% for thoracic organs. Programme-level variation in offer acceptance rates vastly exceeds variation in the traditional, 1-year survival benchmark. Key opportunities to boost utilization include donation after circulatory death and hepatitis C virus (HCV)+ organs; acute kidney injury and suboptimal biopsy kidneys; older and steatotic livers.

SUMMARY

Underutilization of less-than-ideal, yet transplant-worthy organs remains an obstacle to maximizing the impact of the U.S. transplant system. The increased risk of inferior posttransplant outcomes must always be weighed against the risks of remaining on the waitlist. Advanced perfusion technologies; tuning allocation systems for placement efficiency; and data-driven clinical decision support have the potential to increase utilization of medically complex organs.

The association of donor hepatitis C virus infection with 3-year kidney transplant outcomes in the era of direct-acting antiviral medications

To determine the effect of donor hepatitis C virus (HCV) infection on kidney transplant (KT) outcomes in the era of direct-acting antiviral (DAA) medications, we examined 68,087 HCV-negative KT recipients from a deceased donor between March 2015 and May 2021. A Cox regression analysis was used to estimate adjusted hazard ratios (aHRs) of KT failure, incorporating inverse probability of treatment weighting to control for patient selection to receive an HCV-positive kidney (either nucleic acid amplification test positive [NAT+, n = 2331] or antibody positive (Ab+)/NAT- [n = 1826]) based on recipient characteristics. Compared with kidney from HCV-negative donors, those from Ab+/NAT- (aHR = 0.91; 95% confidence interval [CI], 0.75-1.10) and HCV NAT+ (aHR = 0.89; 95% CI, 0.73-1.08) donors were not associated with an increased risk of KT failure over 3 years after transplant. Moreover, HCV NAT+ kidneys were associated with a higher 1-year estimated glomerular filtration (63.0 vs 61.0 mL/min/1.73 m2, P = .007) and lower risk of delayed graft function (aOR = 0.76; 95% CI, 0.68-0.84) compared with HCV-negative kidneys. Our findings suggest that donor HCV positivity is not associated with an elevated risk of graft failure. The inclusion of donor HCV status in the Kidney Donor Risk Index may no longer be appropriate in contemporary practice.

OPTN/SRTR 2021 Annual Data Report: Kidney

The year 2021 marked both successes and challenges for the field of kidney transplantation, in the context of the ongoing COVID-19 pandemic and broader geographic organ distribution. The total number of kidney transplants in the United States reached a record count of 25,487, driven by growth in deceased donor kidney transplants. The total number of candidates listed for deceased donor kidney transplant rose slightly in 2021 but remained below 2019 listing levels, with nearly 10% of candidates having been waiting 5 years or longer. Pretransplant mortality declined slightly among candidates of Black, Hispanic, and other races, in parallel with increasing numbers of Black and Hispanic transplant recipients. In the context of broader organ sharing, there is growing disparity in pretransplant mortality among non-metropolitan compared with metropolitan residents. The proportion of deceased donor kidneys recovered but not used for transplant (nonuse rate) rose to a high of 24.6% overall, with greater nonuse among biopsied kidneys (35.9%), kidneys from donors aged 55 years or older (51.1%), and kidneys with kidney donor profile index (KDPI) of 85% or greater (66.6%). Nonuse of kidneys from donors who are hepatitis C virus (HCV) antibody positive only slightly exceeded that of HCV antibody–negative donors. Disparities in access to living donor kidney transplant persists, especially for non-White and publicly insured patients. Delayed graft function continues an upward trend and occurred in 24% of adult kidney transplants in 2021. Five-year graft survival after living compared with deceased donor transplant was 88.6% versus 80.7% for recipients aged 18-34 years, and 82.1% versus 68.0% for recipients aged 65 years or older. The total number of pediatric kidney transplants performed increased to 820 in 2021, the highest number since 2010. Despite numerous efforts, living donor kidney transplant remains low among pediatric recipients, with continued racial disparities. The rate of deceased donor transplants among pediatric candidates recovered in 2021 from a low in 2020. Congenital anomalies of the kidney and urinary tract remain the leading primary kidney disease diagnosis among pediatric candidates. Most pediatric deceased donor recipients receive a kidney from a donor with KDPI less than 35%. Graft survival continues to improve, with superior outcomes for living donor transplant recipients.

[Current insights on monitoring of renal transplants-Banff and beyond]

Renal transplantation represents the best treatment for end-stage renal disease. Much effort has been invested in improvement of longevity of the transplanted organ including a comprehensive and regularly updated histological scoring system (Banff classification) for surveillance; however, survival of transplanted kidneys is still limited to median 15 years. Molecular analyses have increased the understanding of damaging mechanisms within the transplant, especially antibody-mediated rejection, which can be difficult to identify using histological methods. Changes in the Banff classification necessitate to reclassify biopsies included in studies according to current consensus. Digital and molecular innovations as well as new immunologic mechanisms are anticipated.