New national allocation policy for deceased donor kidneys in the United States and possible effect on patient outcomes

Equity and the operational considerations of the kidney transplant allocation system

PURPOSE OF REVIEW

Demonstrate the impact of allocation system design on access to the waitlist and transplantation for patients with end-stage kidney disease (ESKD).

RECENT FINDINGS

Minoritized groups are more likely to be declined from transplant listing owing to psychosocial criteria. Lack of consistent definitions, screening tools with differential subgroup validity, and insufficient evidence-base contribute to concerns about reliance on psychosocial factors in transplant listing decisions.

SUMMARY

Although kidney transplantation is the preferred treatment choice, a shrinking proportion of prevalent patients are waitlisted for this option in the United States, even among our youngest ESKD patients. Recent HRSA proposals to expand data collection to encompass the prewaitlisting process suggest a timely need to capture additional data on transplant referrals to improve access to transplantation. In 2021, KAS250 was implemented in response to concerns of geographic inequities in transplant rates. However, updates to this system have also resulted in a dramatic rise in organ offers, the number of offers needed to successfully place an organ and lowered utilization rates. Since KAS250, the use of alternative pathways to improve organ utilization rates, such as out-of-sequence placements has increased dramatically across the organ quality spectrum and risk exacerbating disparities in access to transplant. Additionally, the current absence of meaningful oversight risks undermining the perception of the transplant system as an objective process.

SUMMARY

There is a need for a more robust evaluation of recent iterative changes in waitlist and organ allocation practices to ensure equity in access for our most vulnerable patients.

Global transplantation: Lessons from organ transplantation organizations worldwide

Although national transplant organizations share common visions and goals, the creation of a unified global organization remains impractical. Differences in ethnicity, culture, religion, and education shape local practices and infrastructure, making the establishment of a single global entity unfeasible. Even with these social disparities aside, logistical factors such as time and distance between organ procurement and transplantation sites pose significant challenges. While technological advancements have extended organ preservation times, they have yet to support the demands of transcontinental transplantations effectively. This review presents a comparative analysis of the structures, operational frameworks, policies, and legislation governing various transplant organizations around the world. Key differences pertain to the administration of these organizations, trends in organ donation, and organ allocation policies, which reflect the financial, cultural, and religious diversity across different regions. While a global transplant organization may be out of reach, agreeing on best practices for the benefit of patients is essential.

Using Unsupervised Clustering to Characterize Phenotypes Among Older Kidney Transplant Recipients: A Cohort Study

Background

Older kidney transplant recipients have inferior outcomes compared to younger recipients, and this risk may be compounded by donor characteristics.

Objective

We applied an unsupervised machine learning clustering approach to group older recipients into similar phenotypes. We evaluated the association between each cluster and graft failure, and the impact of donor quality on outcomes.

Design

This is a nationally representative retrospective cohort study.

Setting and Patients

Kidney transplant recipients aged ≥65 years identified from the Scientific Registry of Transplant Recipients (2000-2017).

Measurements and Methods

We used unsupervised clustering to generate phenotypes using 16 recipient factors. Donor quality was evaluated using 2 approaches, including the Kidney Donor Risk Index (KDRI). All-cause graft failure was analyzed using multivariable Cox regression.

Results

Overall, 16 364 patients (mean age 69 years; 38% female) were separated into 3 clusters. Cluster 1 recipients were exclusively female; cluster 2 recipients were exclusively males without diabetes; and cluster 3 recipients were males with a higher burden of comorbidities. Compared to cluster 2, the risk of graft failure was higher for cluster 3 recipients (adjusted hazard ratio [aHR] = 1.25, 95% confidence interval [CI] = 1.19-1.32). Cluster 3 recipients of a lower quality (KDRI ≥1.45) kidney had the highest risk of graft failure (aHR = 1.74, 95% CI = 1.61-1.87) relative to cluster 2 recipients of a higher quality kidney.

Limitations

This study did not include an external validation cohort. The findings should be interpreted as exploratory and should not be used to inform individual risk prediction nor be applied to recipients <65 years of age.

Conclusions

In a national cohort of older kidney transplant recipients, unsupervised clustering generated 3 clinically distinct recipient phenotypes. These phenotypes may aid in complementing allocation decisions, providing prognostic information, and optimizing post-transplant care for older recipients.

Access to Transplant for African American and Latino Patients Under the 2014 US Kidney Allocation System

BACKGROUND

Kidney transplant offers better outcomes and reduced costs compared with chronic dialysis. However, racial and ethnic disparities in access to kidney transplant persist despite efforts to expand access to transplant and improve the equity of deceased donor allocation. Our objective was to evaluate after listing the association of race and ethnicity with access to deceased donor kidney transplant (DDKT) after changes to the allocation system in 2014.

METHODS

This retrospective study evaluated access to DDKT after listing since the implementation of the 2014 kidney allocation system. Waitlist status and transplant outcomes were ascertained from data from the Scientific Registry of Transplant Recipients. Our analysis included every adult kidney transplant candidate on the waiting list in the US from January 1, 2015, through June 30, 2023.

RESULTS

A total of 290 763 candidates were on the waiting list for DDKT during the study period. Of these, 36.4% of candidates were African American and 22.2% were Latino. Compared with White non-Latino patients, access to DDKT after listing was reduced for African American (unadjusted hazard ratio [HR], 0.93; 95% confidence interval [CI], 0.92-0.94) and Latino individuals (unadjusted HR, 0.88; 95% CI, 0.87-0.90). After controlling for demographic and clinical factors, these differences in access to transplant widened substantially for African American (HR, 0.78; 95% CI, 0.77-0.80) and Latino patients (HR, 0.73; 95% CI, 0.72-0.74).

CONCLUSIONS

African American and Latino patients had reduced access to DDKT after listing. More effective approaches to improving access for African American and Latino individuals after listing are needed.

A national registry study evaluated the landscape of kidney transplantation among presumed unauthorized immigrants in the United States

Unauthorized immigrants and permanent residents may experience challenges in accessing kidney transplantation due to limited healthcare access, socioeconomic and cultural barriers. Understanding the United States (US) national landscape of kidney transplantation for non-citizens may inform policy changes. To evaluate this, we utilized two cohorts from the US national registry (2013-2023): 287,481 adult candidates for first transplant listing and 190,176 adult first transplant recipients. Citizenship was categorized as US citizen (reference), permanent resident, and presumed unauthorized immigrant. Negative binomial regression was used to quantify the incidence rate ratio over time by citizenship status. Cause-specific hazards models, with clustering at the state of listing/transplant, were used to calculate the adjusted hazard ratio of waitlist mortality, kidney transplant, and post-transplant outcomes (mortality/death-censored graft failure) by citizenship category. The crude proportion of presumed unauthorized immigrants listed increased over time (2013: 0.9%, 2023:1.9%). However, after accounting for case mix and waitlist size, there was no change in listing over time. Presumed unauthorized immigrants were less likely to experience waitlist mortality (adjusted Hazard Ratio 0.54, 95% Confidence Interval: 0.46-0.62), were more likely to obtain deceased donor kidney transplant (1.11: 1.05-1.18), but less likely to receive live donor (0.80: 0.71-0.90) or preemptive kidney transplant (0.52: 0.43-0.62). When stratified by insurance status, presumed unauthorized immigrants on Medicaid were less likely to receive deceased donor kidney transplants compared to their citizen counterparts; however, presumed unauthorized immigrants with private insurance or Medicare were more likely to receive deceased donor kidney transplants. Presumed unauthorized immigrants were less likely to experience post-transplant death (0.56: 0.43-0.69) and graft failure (0.69: 0.57-0.84). Residents had similar pre- and post-transplant outcomes. Despite the barriers to kidney transplantation faced by presumed unauthorized immigrants and residents in the US, better post-transplant outcomes for presumed unauthorized immigrants compared to citizens persisted, even after accounting for differences in patient characteristics.

Deceased Donor Renal Allograft Utility in Adult Single and Multi-organ Transplantation in the United States

Background

Deceased donor multiorgan transplants utilizing kidneys (MOTs) can improve outcomes for multiorgan recipients but reduces kidneys for chronic renal failure patients.

Methods

We reviewed the Organ Procurement and Transplantation Network database from 2015 through 2019, for adult deceased donor kidney transplants. Recipients were classified as kidney transplant alone (KTA) (n = 62,252) or MOTs pancreas-kidney, simultaneous pancreas-kidney (n = 3,976), liver-kidney, simultaneous liver-kidney (n = 3,212), heart-kidney, simultaneous heart-kidney (n = 808), and "other"-kidney, simultaneous "other" kidney (n = 73).

Results

Liver, heart, and lung-alone transplants were at least 7 times more frequent than their MOT correlate, whereas the inverse was true with pancreas transplantation with SPKs being by far the most common pancreas transplant type. On average, KTA recipients waited between 2.8 and 21.4 times longer than MOTs, with SPKs waiting the longest of the MOT types. Predialysis initiation transplants were less frequent in KTAs compared with MOTs. Use of high-quality grafts according to Kidney Donor Profile Index < 35% was frequent among MOTs, but uncommon in KTAs who had an Estimated Post Transplant Survival score (EPTS) of >20%. For recipients older than 65, SPKs and SOKs were rare, but SLKs and SHKs had a higher fraction of recipients than KTAs and were much more likely to use a Kidney Donor Profile Index <35% kidney. SPKs and KTAs with an EPTS ≤20% had the best kidney graft survival. KTAs with an EPTS ≤80% had better kidney graft survival than SLKs, SHKs, and SOKs.

Conclusions

This study highlights disparities in access to deceased donor kidneys for kidney-alone candidates versus MOTs and suggests opportunities to improve allocation.

Canadian Highly Sensitized Patient Program Report: A 1000 Kidney Transplants Story

Purpose

Highly sensitized patients (HSPs) with kidney failure have limited access to kidney transplantation and poorer post-transplant outcomes. Prioritizing HSPs in kidney allocation systems and expanding the pool of deceased donors available to them has helped to reduce their wait times for transplant and enhanced post-transplant outcomes. The Canadian HSP Program was established by Canadian Blood Services in collaboration with provincial organ donation and transplantation programs throughout the country to increase transplant opportunities for transplant candidates needing very specific matches from deceased kidney donors. Highly sensitized patients in the Canadian Program are defined by a calculated panel-reactive antibody (cPRA) ≥95%. In this report, we describe the evolution and trajectory of the Canadian HSP Program and evaluate the national impact on the first 1000 kidney transplant cases.

Source of Information

To allocate deceased donor kidney organs nationally to HSPs and report on the Canadian HSP Program's performance, Canadian Blood Services developed a national database registry known as the Canadian Transplant Registry (CTR) and an online reporting tool known as the Canadian HSP Program Data Dashboard.

Methods

The CTR, which collects HSPs' data for the purpose of matching potential donors to HSPs and as part of required national quality, safety, and efficiency performance measurements, was retrospectively reviewed. Due to the nature of using deidentified aggregate registry data, a patient consent form was not required. A Research Ethical Board (REB) application was also waived.

Key Findings

In this article, we describe the historical development, initial deployment, and evolution of the Canadian HSP Program with a primary aim to increase the rate of deceased donor kidney transplantation. A secondary aim was to evaluate the national impact of the Canadian HSP Program on the first 1000 kidney transplant cases. Transplant candidates who have participated in the Canadian HSP Program and recipients who received transplants were predominantly females (average age 50 years, female 62%) with blood group O (47% of candidates, 42% of transplants). Seventy percent of all active transplant candidates enrolled in the HSP Program were in the hardest to match group (cPRA ≥99%), and only 22% of the transplant candidates with cPRA of 100% have received a transplant to date through the Program. The average times from first participation in the Canadian HSP Program to transplantation for cPRA ≥99% transplant recipients were significantly longer than for cPRA 95% to 98% recipients averaging 22 months versus 6 months, respectively. By the end of June 2024, the Canadian HSP Program had facilitated 1000 transplants, 613 of which were from interprovincial matches. The average (SD) cold ischemic time (CIT) was 14.5 (5.9) hours, with interprovincial transplants exhibiting significantly longer CITs compared with intraprovincial transplants, averaging an additional 4.7 hours.

Limitations

Our study limitations include first that it is a retrospective registry data analysis with no available short- and long-term clinical outcomes data at this point (patient and graft survival). Second, given the nature of registry data, not all relevant data may have been captured and reporting may not be complete for all patients.

Implications

Examination of CTR registry data showed the Canadian HSP Program had a meaningful impact in enabling 1000 HSPs to access transplantation opportunities that may otherwise be unavailable to them.

Inconsistent values and algorithmic fairness: a review of organ allocation priority systems in the United States

BACKGROUND

The Organ Procurement and Transplant Network (OPTN) Final Rule guides national organ transplantation policies, mandating equitable organ allocation and organ-specific priority stratification systems. Current allocation scores rely on mortality predictions.

METHODS

We examined the alignment between the ethical priorities across organ prioritization systems and the statistical design of the risk models in question. We searched PubMed for literature on organ allocation history, policy, and ethics in the United States.

RESULTS

We identified 127 relevant articles, covering kidney (19), liver (60), lung (24), and heart transplants (23), and transplant accessibility (1). Current risk scores emphasize model performance and overlook ethical concerns in variable selection. The inclusion of race, sex, and geographical limits as categorical variables lacks biological basis; therefore, blurring the line between evidence-based models and discrimination. Comprehensive ethical and equity evaluation of risk scores is lacking, with only limited discussion of the algorithmic fairness of the Model for End-Stage Liver Disease (MELD) and the Kidney Donor Risk Index (KDRI) in some literature. We uncovered the inconsistent ethical standards underlying organ allocation scores in the United States. Specifically, we highlighted the exception points in MELD, the inclusion of race in KDRI, the geographical limit in the Lung Allocation Score, and the inadequacy of risk stratification in the Heart Tier system, creating obstacles for medically underserved populations.

CONCLUSIONS

We encourage efforts to address statistical and ethical concerns in organ allocation models and urge standardization and transparency in policy development to ensure fairness, equitability, and evidence-based risk predictions.

Identifying when racial and ethnic disparities arise along the continuum of transplant care: a national registry study

Background

Fewer minoritized patients with end-stage kidney disease (ESKD) receive kidney transplantation (KT); efforts to mitigate disparities have thus far failed. Pinpointing the specific stage(s) within the transplant care continuum (being informed of KT options, joining the waiting list, to receiving KT) where disparities emerge among each minoritized population is pivotal for achieving equity. We therefore quantified racial and ethnic disparities across the KT care continuum.

Methods

We conducted a retrospective cohort study (2015-2020), with follow-up through 12/10/2021. Patients with incident dialysis were identified using the US national registry data. The exposure was race and ethnicity (Asian, Black, Hispanic, and White). We used adjusted modified Poisson regression to quantify the adjusted prevalence ratio (aPR) of being informed of KT, and cause-specific hazards models to calculate adjusted hazard ratios (aHR) of listing, and transplantation after listing.

Findings

Among 637,951 adults initiating dialysis, the mean age (SD) was 63.8 (14.6), 41.8% were female, 5.4% were Asian, 26.3% were Black, 16.6% were Hispanic, and 51.7% were White (median follow-up in years [IQR]:1.92 [0.97-3.39]). Black and Hispanic patients were modestly more likely to be informed of KT (Black: aPR = 1.02, 95% confidence interval [CI]:1.01-1.02; Hispanic: aPR = 1.03, 95% CI: 1.02-1.03) relative to White patients. Asian patients were more likely to be listed (aHR = 1.18, 95% CI: 1.15-1.21) but less likely to receive KT (aHR = 0.56, 95% CI: 0.54-0.58). Both Black and Hispanic patients were less likely to be listed (Black: aHR = 0.87, 95% CI: 0.85-0.88; Hispanic: aHR = 0.85, 95% CI: 0.85-0.88) and receive KT (Black: aHR = 0.61, 95% CI: 0.60-0.63; Hispanic: aHR = 0.64, 95% CI: 0.63-0.66).

Interpretation

Improved characterization of the barriers in KT access specific to each racial and ethnic group, and the interventions to address these distinct challenges throughout the KT care continuum are needed; our findings identify specific stages most in need of mitigation.

Funding

National Institutes of Health.

Outcomes of Older Primary Kidney Transplant Recipients by Induction Agent and High-risk Viral Discordance Status in the United States

Background

The impact of induction type or high-risk viral discordance on older kidney transplant recipients is unclear. Herein, we analyzed the association between induction type, viral discordance, and outcomes for older recipients.

Methods

We analyzed the Scientific Registry of Transplant Recipients standard analysis file for all primary kidney transplant recipients older than 55 y who were transplanted between 2005 and 2022. All transplants were crossmatch negative and ABO-compatible. Recipients were discharged on tacrolimus and mycophenolate ± steroids. Recipients were categorized into 3 groups by induction received: rabbit antithymocyte globulin (r-ATG; N = 51 079), interleukin-2 receptor antagonist (IL-2RA; N = 22 752), and alemtuzumab (N = 13 465). Kaplan-Meier curves were generated for recipient and graft survival, and follow-up was censored at 10 y. Mixed-effect Cox proportional hazard models examined the association between induction type, high-risk viral discordance, and outcomes of interest. Models were adjusted for pertinent recipient and donor characteristics.

Results

Induction type did not predict recipient survival in the multivariable model, whereas Epstein-Barr virus high-risk discordance predicted 14% higher mortality (1.14 [1.07-1.21], P < 0.01). In the multivariable model for death-censored graft survival, alemtuzumab, but not IL-2RA, was associated with an increased risk of graft loss (1.18 [1.06-1.29], P < 0.01) compared with r-ATG. High-risk cytomegalovirus discordance predicted 10% lower death-censored graft survival (1.10 [1.01-1.19], P < 0.02). Live donor and preemptive transplantation were favorable predictors of survival.

Conclusions

In this large cohort of older transplant recipients, alemtuzumab, but not IL-2RA, induction was associated with an increased risk of graft loss compared with r-ATG. Cytomegalovirus and Epstein-Barr virus high-risk viral discordance portended poor graft and recipient survival, respectively.

Advancing Kidney Transplantation: A Machine Learning Approach to Enhance Donor-Recipient Matching

(1) Background: Globally, the kidney donor shortage has made the allocation process critical for patients awaiting a kidney transplant. Adopting Machine Learning (ML) models for donor-recipient matching can potentially improve kidney allocation processes when compared with traditional points-based systems. (2) Methods: This study developed an ML-based approach for donor-recipient matching. A comprehensive evaluation was conducted using ten widely used classifiers (logistic regression, decision tree, random forest, support vector machine, gradient boosting, boost, CatBoost, LightGBM, naive Bayes, and neural networks) across three experimental scenarios to ensure a robust approach. The first scenario used the original dataset, the second used a merged version of the dataset, and the last scenario used a hierarchical architecture model. Additionally, a custom ranking algorithm was designed to identify the most suitable recipients. Finally, the ML-based donor-recipient matching model was integrated into a web-based platform called Nephron. (3) Results: The gradient boost model was the top performer, achieving a remarkable and consistent accuracy rate of 98% across the three experimental scenarios. Furthermore, the custom ranking algorithm outperformed the conventional cosine and Jaccard similarity methods in identifying the most suitable recipients. Importantly, the platform not only facilitated efficient patient selection and prioritisation for kidney allocation but can be flexibly adapted for other solid organ allocation systems built on similar criteria. (4) Conclusions: This study proposes an ML-based approach to optimize donor-recipient matching within the kidney allocation process. Successful implementation of this methodology demonstrates significant potential to enhance both efficiency and fairness in kidney transplantation.

Highly Sensitized Kidney Transplant Outcomes After the 2014 Kidney Allocation System Change

Introduction: Kidney Allocation System (KAS) was implemented by United Network for Organ Sharing in 2014 to reduce allocation disparities. Research Questions: Outcomes of highly sensitized patients (calculated panel reactive antibody (cPRA) ≥ 97%) before and after KAS were compared to low-risk recipients (cPRA <10%) in the post-KAS era were examined. The impact on racial disparities was determined. Design: This was a retrospective study of national registry data. Two cohorts of adult candidates waitlisted for deceased donor transplantation during 3-year periods before and after KAS were identified. Results: Highly sensitized patients (N = 1238 and 4687) received a deceased donor kidney transplant between January 1, 2011 and December 31, 2013 and between January 1, 2015 and December, 31, 2017. Racial disparity for highly sensitized patients improved, yet remained significant (P < 0.001), with Black patients comprising 40% and 41% of the highly sensitized candidates and 28% and 34% of the recipients pre- and post-KAS. While posttransplant death-censored graft failure for highly sensitized recipients was similar overall, post-KAS was associated with improved graft survival in the first year after transplant (HR 0.56, 95% CI 0.40-0.78). When compared to contemporaneous lowrisk recipients, both death-censored and all-cause graft failure were similar for highly sensitized recipients and was associated with increased risk for death-censored graft failure beyond the first year (HR 1.39, 95% CI 1.11-1.73). Conclusion: The allocation system led to an increase in transplantation in highly sensitized candidates without compromising outcomes. Although KAS has led to more balanced transplant rates between highly sensitized Black and White patients, racial inequalities persist.

Kidney Transplant Outcomes From Deceased Donors Who Received Dialysis

Importance

Recipient outcomes after kidney transplant from deceased donors who received dialysis prior to kidney donation are not well described.

Objective

To compare outcomes of transplant recipients who received kidneys from deceased donors who underwent dialysis prior to kidney donation vs recipients of kidneys from deceased donors who did not undergo dialysis.

Design, Setting, and Participants

A retrospective cohort study was conducted including data from 58 US organ procurement organizations on deceased kidney donors and kidney transplant recipients. From 2010 to 2018, 805 donors who underwent dialysis prior to kidney donation were identified. The donors who underwent dialysis prior to kidney donation were matched 1:1 with donors who did not undergo dialysis using a rank-based distance matrix algorithm; 1944 kidney transplant recipients were evaluated.

Exposure

Kidney transplants from deceased donors who underwent dialysis prior to kidney donation compared with kidney transplants from deceased donors who did not undergo dialysis.

Main Outcomes and Measures

The 4 study outcomes were delayed graft function (defined as receipt of dialysis by the kidney recipient ≤1 week after transplant), all-cause graft failure, death-censored graft failure, and death.

Results

From 2010 to 2018, 1.4% of deceased kidney donors (805 of 58 155) underwent dialysis prior to kidney donation. Of these 805 individuals, 523 (65%) donated at least 1 kidney. A total of 969 kidneys (60%) were transplanted and 641 kidneys (40%) were discarded. Among the donors with kidneys transplanted, 514 (mean age, 33 years [SD, 10.8 years]; 98 had hypertension [19.1%] and 36 had diabetes [7%]) underwent dialysis prior to donation and were matched with 514 (mean age, 33 years [SD, 10.9 years]; 98 had hypertension [19.1%] and 36 had diabetes [7%]) who did not undergo dialysis. Kidney transplants from donors who received dialysis prior to donation (n = 954 kidney recipients) were associated with a higher risk of delayed graft function compared with kidney transplants from donors who did not receive dialysis (n = 990 kidney recipients) (59.2% vs 24.6%, respectively; adjusted odds ratio, 4.17 [95% CI, 3.28-5.29]). The incidence rates did not significantly differ at a median follow-up of 34.1 months for all-cause graft failure (43.1 kidney transplants per 1000 person-years from donors who received dialysis prior to donation vs 46.9 kidney transplants per 1000 person-years from donors who did not receive dialysis; adjusted hazard ratio [HR], 0.90 [95% CI, 0.70-1.15]), for death-censored graft failure (22.5 vs 20.6 per 1000 person-years, respectively; adjusted HR, 1.18 [95% CI, 0.83-1.69]), or for death (24.6 vs 30.8 per 1000 person-years; adjusted HR, 0.76 [95% CI, 0.55-1.04]).

Conclusions and Relevance

Compared with receiving a kidney from a deceased donor who did not undergo dialysis, receiving a kidney from a deceased donor who underwent dialysis prior to kidney donation was associated with a significantly higher incidence of delayed graft function, but no significant difference in graft failure or death at follow-up.

Calibration of Priority Points for Sensitization Status of Kidney Transplant Candidates in the United States

Key Points

There are multiple factors associated with high sensitization levels among kidney transplant candidates, which differ by candidate sex. Since the initiation of the kidney allocation system, candidates with higher sensitization have higher rates of deceased donor transplantation. Priority points assigned to candidates associated with sensitization have led to inequities in access to deceased donor transplantation.

Background

A primary change to the national organ allocation system in 2014 for deceased donor kidney offers was to weight candidate priority on the basis of sensitization (i.e ., calculated panel reactive antibody percentage [cPRA%]) using a sliding scale. Increased priority for sensitized patients could improve equity in access to transplantation for disadvantaged candidates. We sought to evaluate the effect of these weights using a contemporary cohort of adult US kidney transplant candidates.

Methods

We used the national Scientific Registry of Transplant Recipients to evaluate factors associated with sensitization using multivariable logistic models and rates of deceased donor transplantation using cumulative incidence models accounting for competing risks and multivariable Cox models.

Results

We examined 270,912 adult candidates placed on the waiting list between January 2016 and September 2023. Six-year cumulative incidence of deceased donor transplantation for candidates with cPRA%=80–85 and 90–95 was 48% and 53%, respectively, as compared with 37% for candidates with cPRA%=0–20. In multivariable models, candidates with high cPRA% had the highest adjusted hazards for deceased donor transplantation. There was significant effect modification such that the association of high cPRA% with adjusted rates of deceased donor transplantation varied by region of the country, sex, race and ethnicity, prior dialysis time, and blood type.

Conclusions

The results indicate that the weighting algorithm for highly sensitized candidates may overinflate the need for prioritization and lead to higher rates of transplantation. Findings suggest recalibration of priority weights for allocation is needed to facilitate overall equity in access to transplantation for prospective kidney transplant candidates. However, priority points should also account for subgroups of candidates who are disadvantaged for access to donor offers.

A2/A2B to B deceased donor kidney transplantation in the Kidney Allocation System era

Kidney transplantation from blood type A2/A2B donors to type B recipients (A2→B) has increased dramatically under the current Kidney Allocation System (KAS). Among living donor transplant recipients, A2-incompatible transplants are associated with an increased risk of all-cause and death-censored graft failure. In light of this, we used data from the Scientific Registry of Transplant Recipients from December 2014 until June 2022 to evaluate the association between A2→B listing and time to deceased donor kidney transplantation (DDKT) and post-DDKT outcomes for A2→B recipients. Among 53 409 type B waitlist registrants, only 12.6% were listed as eligible to accept A2→B offers ("A2-eligible"). The rates of DDKT at 1-, 3-, and 5-years were 32.1%, 61.4%, and 72.1% among A2-eligible candidates and 14.1%, 29.9%, and 44.1% among A2-ineligible candidates, with the former experiencing a 133% higher rate of DDKT (Cox weighted hazard ratio (wHR) = 2.192.332.47; P < .001). The 7-year adjusted mortality was comparable between A2→B and B-ABOc (type B/O donors to B recipients) recipients (wHR 0.780.941.13, P = .5). Moreover, there was no difference between A2→B vs B-ABOc DDKT recipients with regards to death-censored graft failure (wHR 0.771.001.29, P > .9) or all-cause graft loss (wHR 0.820.961.12, P = .6). Following its broader adoption since the implementation of the kidney allocation system, A2→B DDKT appears to be a safe and effective transplant modality for eligible candidates. As such, A2→B listing for eligible type B candidates should be expanded.

Influence of HLA-A, B, and -DRB1 genes and panel-reactive antibodies on the waitlist time for kidney transplantation in the state of Sao Paulo-Brazil

BACKGROUND

Brazil ranks second in the absolute number of transplants. However, the supply remains insufficient to meet the demands, resulting in a lengthy waitlist. This study aimed to analyze whether the frequency of human leukocyte antigen (HLA) and the value of calculated panel reactive antibody (cPRA) would influence the waiting time for kidney transplantation.

METHODS

The HLA-A, B, and -DRB1 frequencies and the cPRA value were analyzed in 11,186 kidney transplant candidates included in the waitlist from 2006 to 2016.

RESULTS

The most frequent alleles were HLA-A*02, HLA-B*35, and HLA-DRB1*13. The overall mean length of stay on the list was 986 ± 1001 days. The mean waiting time for the three most frequent alleles of the HLA-A and B loci showed no significant difference when compared with the least frequent alleles; however, for the HLA-DRB1 locus, the most frequent alleles showed a shorter waiting time. In the association between HLA and PRA, the average length of stay on the list increased according to the candidate's degree of sensitization, regardless of the analyzed HLA frequency.

CONCLUSION

The length of stay on the waitlist is influenced by the frequency of the HLA alleles of the DRB1 locus and the degree of sensitization.

Prognostic Models in Nephrology: Where Do We Stand and Where Do We Go from Here? Mapping Out the Evidence in a Scoping Review

Prognostic models can strongly support individualized care provision and well-informed shared decision making. There has been an upsurge of prognostic research in the field of nephrology, but the uptake of prognostic models in clinical practice remains limited. Therefore, we map out the research field of prognostic models for kidney patients and provide directions on how to proceed from here. We performed a scoping review of studies developing, validating, or updating a prognostic model for patients with CKD. We searched all published models in PubMed and Embase and report predicted outcomes, methodological quality, and validation and/or updating efforts. We found 602 studies, of which 30.1% concerned CKD populations, 31.6% dialysis populations, and 38.4% kidney transplantation populations. The most frequently predicted outcomes were mortality ( n =129), kidney disease progression ( n =75), and kidney graft survival ( n =54). Most studies provided discrimination measures (80.4%), but much less showed calibration results (43.4%). Of the 415 development studies, 28.0% did not perform any validation and 57.6% performed only internal validation. Moreover, only 111 models (26.7%) were externally validated either in the development study itself or in an independent external validation study. Finally, in 45.8% of development studies no useable version of the model was reported. To conclude, many prognostic models have been developed for patients with CKD, mainly for outcomes related to kidney disease progression and patient/graft survival. To bridge the gap between prediction research and kidney patient care, patient-reported outcomes, methodological rigor, complete reporting of prognostic models, external validation, updating, and impact assessment urgently need more attention.

Strategies to Guide Preemptive Waitlisting and Equity in Waittime Accrual by Race/Ethnicity

BACKGROUND

Use of eGFR to determine preemptive waitlisting eligibility may contribute to racial/ethnic disparities in access to waitlisting, which can only occur when the eGFR falls to ≤20 ml/min per 1.73 m 2 . Use of an alternative risk-based strategy for waitlisting may reduce these inequities ( e.g. , a kidney failure risk equation [KFRE] estimated 2-year risk of kidney failure) rather than the standard eGFR threshold for determining waitlist eligibility. Our objective was to model the amount of preemptive waittime that could be accrued by race and ethnicity, applying two different strategies to determine waitlist eligibility.

METHODS

Using electronic health record data, linear mixed models were used to compare racial/ethnic differences in preemptive waittime that could be accrued using two strategies: estimating the time between an eGFR ≤20 and 5 ml/min per 1.73 m 2 versus time between a 25% 2-year predicted risk of kidney failure (using the KFRE, which incorporates age, sex, albuminuria, and eGFR to provide kidney failure risk estimation) and eGFR of 5 ml/min per 1.73 m 2 .

RESULTS

Among 1290 adults with CKD stages 4-5, using the Chronic Kidney Disease Epidemiology Collaboration equation yielded shorter preemptive waittime between an eGFR of 20 and 5 ml/min per 1.73 m 2 in Black (-6.8 months; 95% confidence interval [CI], -11.7 to -1.9), Hispanic (-10.2 months; -15.3 to -5.1), and Asian/Pacific Islander (-10.3 months; 95% CI, -15.3 to -5.4) patients compared with non-Hispanic White patients. Use of a KFRE threshold to determine waittime yielded smaller differences by race and ethnicity than observed when using a single eGFR threshold, with shorter time still noted for Black (-2.5 months; 95% CI, -7.8 to 2.7), Hispanic (-4.8 months; 95% CI, -10.3 to 0.6), and Asian/Pacific Islander (-5.4 months; -10.7 to -0.1) individuals compared with non-Hispanic White individuals, but findings only met statistical significance criteria in Asian/Pacific Islander individuals. When we compared potential waittime availability using a KFRE versus eGFR threshold, use of the KFRE yielded more equity in waittime for Black ( P = 0.02), Hispanic ( P = 0.002), and Asian/Pacific Islander ( P = 0.002) patients.

CONCLUSIONS

Use of a risk-based strategy was associated with greater racial equity in waittime accrual compared with use of a standard single eGFR threshold to determine eligibility for preemptive waitlisting.

Predicting Kidney Transplantation Outcomes from Donor and Recipient Characteristics at Time Zero: Development of a Mobile Application for Nephrologists

(1) Background: We report on the development of a predictive tool that can estimate kidney transplant survival at time zero. (2) Methods: This was an observational, retrospective study including 5078 transplants. Death-censored graft and patient survivals were calculated. (3) Results: Graft loss was associated with donor age (hazard ratio [HR], 1.021, 95% confidence interval [CI] 1.018-1.024, p < 0.001), uncontrolled donation after circulatory death (DCD) (HR 1.576, 95% CI 1.241-2.047, p < 0.001) and controlled DCD (HR 1.567, 95% CI 1.372-1.812, p < 0.001), panel reactive antibody percentage (HR 1.009, 95% CI 1.007-1.011, p < 0.001), and previous transplants (HR 1.494, 95% CI 1.367-1.634, p < 0.001). Patient survival was associated with recipient age (> 60 years, HR 5.507, 95% CI 4.524-6.704, p < 0.001 vs. < 40 years), donor age (HR 1.019, 95% CI 1.016-1.023, p < 0.001), dialysis vintage (HR 1.0000263, 95% CI 1.000225-1.000301, p < 0.01), and male sex (HR 1.229, 95% CI 1.135-1.332, p < 0.001). The C-statistics for graft and patient survival were 0.666 (95% CI: 0.646, 0.686) and 0.726 (95% CI: 0.710-0.742), respectively. (4) Conclusions: We developed a mobile app to estimate survival at time zero, which can guide decisions for organ allocation.

Implementation of the ASCENT Trial to Improve Transplant Waitlisting Access

Introduction

The Allocation System for changes in Equity in Kidney Transplantation (ASCENT) study was a hybrid type 1 trial of a multicomponent intervention among 655 US dialysis facilities with low kidney transplant waitlisting to educate staff and patients about kidney allocation system (KAS) changes and increase access to and reduce racial disparities in waitlisting. Intervention components included a staff webinar, patient and staff educational videos, and facility-specific feedback reports.

Methods

Implementation outcomes were assessed using the Reach, Effectiveness, Adoption, Implementation, and Maintenance Framework. Postimplementation surveys were administered among intervention group facilities (n = 334); interviews were conducted with facility staff (n = 6). High implementation was defined as using 3 to 4 intervention components, low implementation as using 1 to 2 components, and nonimplementation as using no components.

Results

A total of 331 (99%) facilities completed the survey; 57% were high implementers, 31% were low implementers, and 12% were nonimplementers. Waitlisting events were higher or similar among high versus low implementer facilities for incident and prevalent populations; for Black incident patients, the mean proportion waitlisted in low implementer facilities was 0.80% (95% confidence interval [CI]: 0.73-0.87) at baseline and 0.55% at 1-year (95% CI: 0.48-0.62) versus 0.83% (95% CI: 0.78-0.88) at baseline and 1.40% at 1-year (95% CI: 1.35-1.45) in high implementer facilities. Interviews revealed that the intervention helped facilities prioritize transplant education, but that intervention components were not uniformly shared.

Conclusion

The findings provide important context to interpret ASCENT effectiveness results and identified key barriers and facilitators to consider for future modification and scale-up of multilevel, multicomponent interventions in dialysis settings.

Increasing Access to Kidney Transplantation for Black and Asian Patients Through Modification of the Current A2 to B Allocation Policy

Key Points

A2 to B incompatible transplantation is not fully practiced in the country, and further policies should encourage centers to perform more blood incompatible transplants. Centers that currently practice A2 to B incompatible transplants should give priority to blood type B patients who are willing to accept an A organ. This will benefit Asian and Black patients.

Background

The rate of A2 to B incompatible (ABO-i) kidney transplant continues to be low despite measures in the new kidney allocation system (KAS) to facilitate such transplants. This study shows how the number of ABO-i transplants could increase if KAS policies were used to their fullest extent through a boost in ABO-i priority points.

Method

Transplant outcomes were predicted using the Kidney Pancreas Simulated Allocation Model, preloaded with national data of 2010. We used this simulation to compare KAS with a new intervention in which priority equal to cPRA=100 has been given to blood type B candidates who are willing to accept an A blood type organ.

Results

The number of Black recipients increased by 375 (from 35% of the total recipient population to 38.7%), the number of blood type B Blacks increased by 65 (from 8% of the total recipient population to 9%), and the number of blood type B Black patients receiving blood type A kidneys increased by 49 (from 2% of the total recipient population to 2.5%). The same change occurred for Asians, particularly blood type B Asians (from 0.54% of the total recipient population to 0.7%). The average wait time notably decreased by 27 days for blood type B Black patients. In the proposed scenario, 263 blood type B Black patients received a blood type A organ (2.5% of the total recipient population) while only 181 (1.1%) of such transplants were performed in 2021. These results signify a considerable opportunity loss of ABO-i transplants for Black patients.

Conclusions

If this policy was universally adopted, we would expect to see an overall increase in A2 to B transplantation, but in reality, not all centers perform ABO-i transplantation. Thus, adopting this policy would incentivize other centers to perform more subtyping of A-type kidneys, and it would increase access to organs for blood type B Asian and Black patients in centers where ABO-i transplantation already takes place.

Longevity Matching for Living Donor Renal Transplantation

INTRODUCTION

This study identifies the effect of individual donor and recipient characteristics on graft survival in living-donor kidney transplantation (LDKT) using a recently described novel measure, kidney life years (KLYs).

MATERIALS AND METHODS

The Organ Procurement and Transplantation Network/United Network for Organ Sharing database was used to identify first-time kidney-only LDKT recipients between 1987 and 2020 who did not experience death with a functioning graft (DWFG) and were not missing relevant information (n = 87,290). Patient characteristics were evaluated using Cox and multiple regression analyses, with the dependent variable being KLYs. An equation for expected KLYs based on patient characteristics was created using regression coefficients. The equation was validated using bootstrapped Pearson correlations and then applied to the DWFG group for comparison.

RESULTS

Based on statistical significance from Cox and multiple linear regression analyses, 9 of the original 18 variables were selected for inclusion in the equation. Variables with notable impact included HLA match points (0.021 KLYs; 95% CI: [0.019,0.024]; P ≤ .001), Donor Age (-0.030 KLYs; 95% CI: [-0.035,-0.025]; P ≤ .001), and Donor African American Ethnicity (-2.356 KLYs; 95% CI: [-2.552,-2.159]; P ≤ .001). Equation validation was supported, given a negative correlation (r = -0.071; P ≤ .001) between expected KLY change and observed graft failure. Expected KLY change was found to be greater in those who eventually DWFG when compared with all other LDKTs (t = -5.735, P ≤ .001).

CONCLUSIONS

Increasing HLA match points may be more beneficial for graft longevity than minimizing donor age in comparisons using realistic between-donor differences. Additionally, greater average expected KLYs in those who ultimately DWFG may illustrate an opportunity for improved donor-recipient matching.

Continuous allocation: The problem with EPTS and pediatric kidney candidates

BACKGROUND

The 2014 Kidney Allocation System (KAS) introduced longevity matching for adult candidates using the Estimated Post-Transplant Survival (EPTS) score, which includes candidate age, time on dialysis, diabetes status, and number of previous solid organ transplants. The proposed continuous distribution framework may expand the use of this attribute to pediatric candidates, but there is no data on its performance among pediatric kidney transplant recipients.

METHODS

We performed a retrospective cohort study of 6800 pediatric kidney transplant recipients from 2001 to 2011 using Organ Procurement and Transplantation Network (OPTN) data. EPTS score was calculated for each patient and compared to reported patient survival to estimate the validity of the score in children.

RESULTS

The median age of patients was 14.01 years (IQR 9.29-16.37 years), and dialysis vintage was 0.67 years (IQR 0-1.82 years). 18.2% of the cohort had a prior transplant and 1% had diabetes. Median EPTS score was 2 (IQR 1-2). Seven percent of patients died during the study period and 54.7% of the cohort was censored prior to 10 years. The c-statistic was 0.505 (95% CI: 0.49-0.53).

CONCLUSION

Overall, EPTS is not a valid predictor of patient survival among pediatric kidney transplant recipients.

Predicting kidney transplant survival using multiple feature representations for HLAs

Kidney transplantation can significantly enhance living standards for people suffering from end-stage renal disease. A significant factor that affects graft survival time (the time until the transplant fails and the patient requires another transplant) for kidney transplantation is the compatibility of the Human Leukocyte Antigens (HLAs) between the donor and recipient. In this paper, we propose 4 new biologically-relevant feature representations for incorporating HLA information into machine learning-based survival analysis algorithms. We evaluate our proposed HLA feature representations on a database of over 100,000 transplants and find that they improve prediction accuracy by about 1%, modest at the patient level but potentially significant at a societal level. Accurate prediction of survival times can improve transplant survival outcomes, enabling better allocation of donors to recipients and reducing the number of re-transplants due to graft failure with poorly matched donors.

Discrepant Outcomes between National Kidney Transplant Data Registries in the United States

SIGNIFICANCE STATEMENT

Effects of reduced access to external data by transplant registries to improve accuracy and completeness of the collected data are compounded by different data management processes at three US organizations that maintain kidney transplant-related datasets. This analysis suggests that the datasets have large differences in reported outcomes that vary across different subsets of patients. These differences, along with recent disclosure of previously missing outcomes data, raise important questions about completeness of the outcome measures. Differences in recorded deaths seem to be increasing in recent years, reflecting the adverse effects of restricted access to external data sources. Although these registries are invaluable sources for the transplant community, discrepancies and incomplete reporting risk undermining their value for future analyses, particularly when used for developing national transplant policy or regulatory measures.

BACKGROUND

Central to a transplant registry's quality are accuracy and completeness of the clinical information being captured, especially for important outcomes, such as graft failure or death. Effects of more limited access to external sources of death data for transplant registries are compounded by different data management processes at the United Network for Organ Sharing (UNOS), the Scientific Registry of Transplant Recipients (SRTR), and the United States Renal Data System (USRDS).

METHODS

This cross-sectional registry study examined differences in reported deaths among kidney transplant candidates and recipients of kidneys from deceased and living donors in 2000 through 2019 in three transplant datasets on the basis of data current as of 2020. We assessed annual death rates and survival estimates to visualize trends in reported deaths between sources.

RESULTS

The UNOS dataset included 77,605 deaths among 315,346 recipients and 61,249 deaths among 275,000 nonpreemptively waitlisted candidates who were never transplanted. The SRTR dataset included 87,149 deaths among 315,152 recipients and 60,042 deaths among 259,584 waitlisted candidates. The USRDS dataset included 89,515 deaths among 311,955 candidates and 63,577 deaths among 238,167 waitlisted candidates. Annual death rates among the prevalent transplant population show accumulating differences across datasets-2.31%, 4.00%, and 4.03% by 2019 from UNOS, SRTR, and USRDS, respectively. Long-term survival outcomes were similar among nonpreemptively waitlisted candidates but showed more than 10% discordance between USRDS and UNOS among transplanted patients.

CONCLUSIONS

Large differences in reported patient outcomes across datasets seem to be increasing, raising questions about their completeness. Understanding the differences between these datasets is essential for accurate, reliable interpretation of analyses that use these data for policy development, regulatory oversight, and research.

PODCAST

This article contains a podcast at https://dts.podtrac.com/redirect.mp3/www.asn-online.org/media/podcast/JASN/2023_10_24_JASN0000000000000194.mp3.

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.

Exploring the variable importance in random forests under correlations: a general concept applied to donor organ quality in post-transplant survival

Random Forests are a powerful and frequently applied Machine Learning tool. The permutation variable importance (VIMP) has been proposed to improve the explainability of such a pure prediction model. It describes the expected increase in prediction error after randomly permuting a variable and disturbing its association with the outcome. However, VIMPs measure a variable's marginal influence only, that can make its interpretation difficult or even misleading. In the present work we address the general need for improving the explainability of prediction models by exploring VIMPs in the presence of correlated variables. In particular, we propose to use a variable's residual information for investigating if its permutation importance partially or totally originates from correlated predictors. Hypotheses tests are derived by a resampling algorithm that can further support results by providing test decisions and p-values. In simulation studies we show that the proposed test controls type I error rates. When applying the methods to a Random Forest analysis of post-transplant survival after kidney transplantation, the importance of kidney donor quality for predicting post-transplant survival is shown to be high. However, the transplant allocation policy introduces correlations with other well-known predictors, which raises the concern that the importance of kidney donor quality may simply originate from these predictors. By using the proposed method, this concern is addressed and it is demonstrated that kidney donor quality plays an important role in post-transplant survival, regardless of correlations with other predictors.

Evaluating the outcomes of donor-recipient age differences in young adults undergoing liver transplantation

The current liver allocation system may be disadvantaging younger adult recipients as it does not incorporate the donor-recipient age difference. Given the longer life expectancy of younger recipients, the influences of older donor grafts on their long-term prognosis should be elucidated. This study sought to reveal the long-term prognostic influence of the donor-recipient age difference in young adult recipients. Adult patients who received initial liver transplants from deceased donors between 2002 and 2021 were identified from the UNOS database. Young recipients (patients 45 years old or below) were categorized into 4 groups: donor age younger than the recipient, 0-9 years older, 10-19 years older, or 20 years older or above. Older recipients were defined as patients 65 years old or above. To examine the influence of the age difference in long-term survivors, conditional graft survival analysis was conducted on both younger and older recipients. Among 91,952 transplant recipients, 15,170 patients were 45 years old or below (16.5%); these were categorized into 6,114 (40.3%), 3,315 (21.9%), 2,970 (19.6%), and 2,771 (18.3%) for groups 1-4, respectively. Group 1 demonstrated the highest probability of survival, followed by groups 2, 3, and 4 for the actual graft survival and conditional graft survival analyses. In younger recipients who survived at least 5 years post-transplant, inferior long-term survival was observed when there was an age difference of 10 years or above (86.9% vs. 80.6%, log-rank p <0.01), whereas there was no difference in older recipients (72.6% vs. 74.2%, log-rank p =0.89). In younger patients who are not in emergent need of a transplant, preferential allocation of younger aged donor offers would optimize organ utility by increasing postoperative graft survival time.

Increasing Kidney-Exchange Options Within the Existing Living Donor Pool With CIAT: A Pilot Implementation Study

Computerized integration of alternative transplantation programs (CIAT) is a kidney-exchange program that allows AB0- and/or HLA-incompatible allocation to difficult-to-match patients, thereby increasing their chances. Altruistic donors make this available for waiting list patients as well. Strict criteria were defined for selected highly-immunized (sHI) and long waiting (LW) candidates. For LW patients AB0i allocation was allowed. sHI patients were given priority and AB0i and/or CDC cross-match negative HLAi allocations were allowed. A local pilot was established between 2017 and 2022. CIAT results were assessed against all other transplant programs available. In the period studied there were 131 incompatible couples; CIAT transplanted the highest number of couples (35%), compared to the other programs. There were 55 sHI patients; CIAT transplanted as many sHI patients as the Acceptable Mismatch program (18%); Other programs contributed less. There were 69 LW patients; 53% received deceased donor transplantations, 20% were transplanted via CIAT. In total, 72 CIAT transplants were performed: 66 compatible, 5 AB0i and 1 both AB0i and HLAi. CIAT increased opportunities for difficult-to-match patients, not by increasing pool size, but through prioritization and allowing AB0i and "low risk" HLAi allocation. CIAT is a powerful addition to the limited number of programs available for difficult-to-match patients.

The UK kidney donor risk index poorly predicts long-term transplant survival in paediatric kidney transplant recipients

Background

The UK kidney offering scheme introduced a kidney donor risk index (UK-KDRI) to improve the utility of deceased-donor kidney allocations. The UK-KDRI was derived using adult donor and recipient data. We assessed this in a paediatric cohort from the UK transplant registry.

Methods

We performed Cox survival analysis on first kidney-only deceased brain-dead transplants in paediatric (<18 years) recipients from 2000-2014. The primary outcome was death-censored allograft survival >30 days post-transplant. The main study variable was UK-KDRI derived from seven donor risk-factors, categorised into four groups (D1-low risk, D2, D3 and D4-highest risk). Follow-up ended on 31-December-2021.

Results

319/908 patients experienced transplant loss with rejection as the main cause (55%). The majority of paediatric patients received donors from D1 donors (64%). There was an increase in D2-4 donors during the study period, whilst the level of HLA mismatching improved. The KDRI was not associated with allograft failure. In multi-variate analysis, increasing recipient age [adjusted HR and 95%CI: 1.05(1.03-1.08) per-year, p<0.001], recipient minority ethnic group [1.28(1.01-1.63), p<0.05), dialysis before transplant [1.38(1.04-1.81), p<0.005], donor height [0.99 (0.98-1.00) per centimetre, p<0.05] and level of HLA mismatch [Level 3: 1.92(1.19-3.11); Level 4: 2.40(1.26-4.58) versus Level 1, p<0.01] were associated with worse outcomes. Patients with Level 1 and 2 HLA mismatches (0 DR +0/1 B mismatch) had median graft survival >17 years regardless of UK-KDRI groups. Increasing donor age was marginally associated with worse allograft survival [1.01 (1.00-1.01) per year, p=0.05].

Summary

Adult donor risk scores were not associated with long-term allograft survival in paediatric patients. The level of HLA mismatch had the most profound effect on survival. Risk models based on adult data alone may not have the same validity for paediatric patients and therefore all age-groups should be included in future risk prediction models.

Characterization of Transplant Center Decisions to Allocate Kidneys to Candidates With Lower Waiting List Priority

Importance

Allocation of deceased donor kidneys is meant to follow a ranked match-run list of eligible candidates, but transplant centers with a 1-to-1 relationship with their local organ procurement organization have full discretion to decline offers for higher-priority candidates and accept them for lower-ranked candidates at their center.

Objective

To describe the practice and frequency of transplant centers placing deceased donor kidneys with candidates who are not the highest rank at their center according to the allocation algorithm.

Design, Setting, and Participants

This retrospective cohort study used 2015 to 2019 organ offer data from US transplant centers with a 1-to-1 relationship with their local organ procurement organization, following candidates for transplant events from January 2015 to December 2019. Participants were deceased kidney donors with a single match-run and at least 1 kidney transplanted locally and adult, first-time, kidney-only transplant candidates receiving at least 1 offer for a locally transplanted deceased donor kidney. Data were analyzed from March 1, 2022 to March 28, 2023.

Exposure

Demographic and clinical characteristics of donors and recipients.

Main Outcomes and Measures

The outcome of interest was kidney transplantation into the highest-priority candidate (defined as transplanted after zero declines for local candidates in the match-run) vs a lower-ranked candidate.

Results

This study assessed 26 579 organ offers from 3136 donors (median [IQR] age, 38 [25-51] years; 2903 [62%] men) to 4668 recipients. Transplant centers skipped their highest-ranked candidate to place kidneys further down the match-run for 3169 kidneys (68%). These kidneys went to a median (IQR) of the fourth- (third- to eighth-) ranked candidate. Higher kidney donor profile index (KDPI; higher score indicates lower quality) kidneys were less likely to go to the highest-ranked candidate, with 24% of kidneys with KDPI of at least 85% going to the top-ranked candidate vs 44% of KDPI 0% to 20% kidneys. When comparing estimated posttransplant survival (EPTS) scores between the skipped candidates and the ultimate recipients, kidneys were placed with recipients with both better and worse EPTS than the skipped candidates, across all KDPI risk groups.

Conclusions and Relevance

In this cohort study of local kidney allocation at isolated transplant centers, we found that centers frequently skipped their highest-priority candidates to place kidneys further down the allocation prioritization list, often citing organ quality concerns but placing kidneys with recipients with both better and worse EPTS with nearly equal frequency. This occurred with limited transparency and highlights the opportunity to improve the matching and offer algorithm to improve allocation efficiency.

Organ donation by children in Australia, 2000-2019: impact of the 2009 National Reform Program. A population-based registry data study

OBJECTIVES

To assess the impact of the 2009 National Reform Program for organ donation in Australia on the number and characteristics of organ donors under 16 years of age.

DESIGN, SETTING, PARTICIPANTS

Retrospective observational time series study; analysis of Australia and New Zealand Organ Donation (ANZOD) registry data for all consented potential deceased organ donors under 16 years of age during 2000-2019, and of numbers of donors aged 16 years or more reported in ANZOD annual reports.

MAIN OUTCOME MEASURES

Difference between 2000-2008 (pre-reform) and 2009-2019 (reform period) in annual organ donor rates (donors per million population), by age group (under 16 years, 16 years or more), reported as incidence rate ratio (IRR).

SECONDARY OUTCOMES

Differences in child donor characteristics during 2000-2008 and 2009-2019.

RESULTS

During 2000-2019, 400 children under 16 years of age were consented potential deceased organ donors, of whom 374 were actual deceased donors (94%): 146 during 2000-2008, 228 during 2009-2019. The median annual rate was 3.3 (interquartile range [IQR], 3.0-4.3) actual donors per million population during 2000-2008 and 4.2 (IQR, 3.6-5.2) donors per million population during 2009-2019 (IRR, 1.15; 95% confidence interval [CI], 0.93-1.42). In contrast, the difference between the two periods was statistically significant for donors aged 16 years or more, rising from 11.7 (IQR, 11.2-11.8) to 19.9 (IQR, 18.3-24.4) actual donors per million population (IRR, 1.75; 95% CI, 1.66-1.85). The median age of actual organ donors under 16 was similar during 2000-2008 (11 years; IQR, 7-14 years) and 2009-2019 (10 years; IQR, 4-14 years), as was the proportion of donors in this age group under 10 kg (2000-2008: four of 146, 3%; 2009-2019: 14 of 228, 6%).

CONCLUSIONS

Despite its overall effect on organ donation rates, the National Reform Program was not effective in increasing the numbers of donors under 16 years of age. Relying on broad initiatives for adult donors may not be appropriate for achieving this aim.

The Benefits of Preemptive Transplantation Using High-Kidney Donor Profile Index Kidneys

BACKGROUND

The Kidney Donor Profile Index (KDPI) is a percentile score summarizing the likelihood of allograft failure: A KDPI ≥85% is associated with shorter allograft survival, and 50% of these donated kidneys are not currently used for transplantation. Preemptive transplantation (transplantation without prior maintenance dialysis) is associated with longer allograft survival than transplantation after dialysis; however, it is unknown whether this benefit extends to high-KDPI transplants. The objective of this analysis was to determine whether the benefit of preemptive transplantation extends to recipients of transplants with a KDPI ≥85%.

METHODS

This retrospective cohort study compared the post-transplant outcomes of preemptive and nonpreemptive deceased donor kidney transplants using data from the Scientific Registry of Transplant Recipients. 120,091 patients who received their first, kidney-only transplant between January 1, 2005, and December 31, 2017, were studied, including 23,211 with KDPI ≥85%. Of this cohort, 12,331 patients received a transplant preemptively. Time-to-event models for the outcomes of allograft loss from any cause, death-censored graft loss, and death with a functioning transplant were performed.

RESULTS

Compared with recipients of nonpreemptive transplants with a KDPI of 0%-20% as the reference group, the risk of allograft loss from any cause in recipients of a preemptive transplant with KDPI ≥85% (hazard ratio [HR], 1.51; 95% confidence interval [CI], 1.39 to 1.64) was lower than that in recipients of nonpreemptive transplant with a KDPI ≥85% (HR, 2.39; 95% CI, 2.21 to 2.58) and similar to that of recipients of a nonpreemptive transplant with a KDPI of 51%-84% (HR, 1.61; 95% CI, 1.52 to 1.70).

CONCLUSIONS

Preemptive transplantation is associated with a lower risk of allograft failure, irrespective of KDPI, and preemptive transplants with KDPI ≥85% have comparable outcomes with nonpreemptive transplants with KDPI 51%-84%.

Kidney organ allocation: reducing discards

PURPOSE OF REVIEW

The donation and kidney transplant system in the United States is challenged with reducing the number of kidneys that are procured for transplant but ultimately discarded. That number can reach 20% of donated kidneys each year.

RECENT FINDINGS

The reasons for these discards, in the face of overwhelming demand, are multiple.

SUMMARY

The authors review the data supporting a number of potential causes for high discard rates as well as provide potential solutions to the problem.

A Primer in Precision Nephrology: Optimizing Outcomes in Kidney Health and Disease through Data-Driven Medicine

This year marks the 63rd anniversary of the International Society of Nephrology, which signaled nephrology's emergence as a modern medical discipline. In this article, we briefly trace the course of nephrology's history to show a clear arc in its evolution-of increasing resolution in nephrological data-an arc that is converging with computational capabilities to enable precision nephrology. In general, precision medicine refers to tailoring treatment to the individual characteristics of patients. For an operational definition, this tailoring takes the form of an optimization, in which treatments are selected to maximize a patient's expected health with respect to all available data. Because modern health data are large and high resolution, this optimization process requires computational intervention, and it must be tuned to the contours of specific medical disciplines. An advantage of this operational definition for precision medicine is that it allows us to better understand what precision medicine means in the context of a specific medical discipline. The goal of this article was to demonstrate how to instantiate this definition of precision medicine for the field of nephrology. Correspondingly, the goal of precision nephrology was to answer two related questions: ( 1 ) How do we optimize kidney health with respect to all available data? and ( 2 ) How do we optimize general health with respect to kidney data?

Downregulation of KLF10 contributes to the regeneration of survived renal tubular cells in cisplatin-induced acute kidney injury via ZBTB7A-KLF10-PTEN axis

Acute kidney injury (AKI) is a common clinical dysfunction with complicated pathophysiology and limited therapeutic methods. Renal tubular injury and the following regeneration process play a vital role in the course of AKI, but the underlining molecular mechanism remains unclear. In this study, network-based analysis of online transcriptional data of human kidney found that KLF10 was closely related to renal function, tubular injury and regeneration in various renal diseases. Three classical mouse models confirmed the downregulation of KLF10 in AKI and its correlation with tubular regeneration and AKI outcome. The 3D renal tubular model in vitro and fluorescent visualization system of cellular proliferation were constructed to show that KLF10 declined in survived cells but increased during tubular formation or conquering proliferative impediment. Furthermore, overexpression of KLF10 significantly inhibited, whereas knockdown of KLF10 extremely promoted the capacity of proliferation, injury repairing and lumen-formation of renal tubular cells. In mechanism, PTEN/AKT pathway were validated as the downstream of KLF10 and participated in its regulation of tubular regeneration. By adopting proteomic mass spectrum and dual-luciferase reporter assay, ZBTB7A were found to be the upstream transcription factor of KLF10. Our findings suggest that downregulation of KLF10 positively contributed to tubular regeneration in cisplatin induced acute kidney injury via ZBTB7A-KLF10-PTEN axis, which gives insight into the novel therapeutic and diagnostical target of AKI.

Hypothermia or Machine Perfusion in Kidney Donors

BACKGROUND

Therapeutic hypothermia in brain-dead organ donors has been shown to reduce delayed graft function in kidney recipients after transplantation. Data are needed on the effect of hypothermia as compared with machine perfusion on outcomes after kidney transplantation.

METHODS

At six organ-procurement facilities in the United States, we randomly assigned brain-dead kidney donors to undergo therapeutic hypothermia (hypothermia group), ex situ kidney hypothermic machine perfusion (machine-perfusion group), or both (combination-therapy group). The primary outcome was delayed graft function in the kidney transplant recipients (defined as the initiation of dialysis during the first 7 days after transplantation). We also evaluated whether hypothermia alone was noninferior to machine perfusion alone and whether the combination of both methods was superior to each of the individual therapies. Secondary outcomes included graft survival at 1 year after transplantation.

RESULTS

From 725 enrolled donors, 1349 kidneys were transplanted: 359 kidneys in the hypothermia group, 511 in the machine-perfusion group, and 479 in the combined-therapy group. Delayed graft function occurred in 109 patients (30%) in the hypothermia group, in 99 patients (19%) in the machine-perfusion group, and in 103 patients (22%) in the combination-therapy group. Adjusted risk ratios for delayed graft function were 1.72 (95% confidence interval [CI], 1.35 to 2.17) for hypothermia as compared with machine perfusion, 1.57 (95% CI, 1.26 to 1.96) for hypothermia as compared with combination therapy, and 1.09 (95% CI, 0.85 to 1.40) for combination therapy as compared with machine perfusion. At 1 year, the frequency of graft survival was similar in the three groups. A total of 10 adverse events were reported, including cardiovascular instability in 9 donors and organ loss in 1 donor owing to perfusion malfunction.

CONCLUSIONS

Among brain-dead organ donors, therapeutic hypothermia was inferior to machine perfusion of the kidney in reducing delayed graft function after transplantation. The combination of hypothermia and machine perfusion did not provide additional protection. (Funded by Arnold Ventures; ClinicalTrials.gov number, NCT02525510.).

Reexamining the Impact of Insurance Type on Kidney Transplant Waitlist Status and Posttransplantation Outcomes in the United States After Implementation of the Affordable Care Act

Insurance type, a marker of socioeconomic status, has been associated with poor access to kidney transplant (KT) and worse KT outcomes before the implementation of the Affordable Care Act (ACA) and the revised Kidney Allocation System (KAS). In this study, we assessed if insurance type remained a risk marker for worse waitlist and transplant outcomes after ACA and KAS.

Methods

Using Scientific Registry of Transplant Recipients data, we assessed insurance type of waitlisted candidates pre- (2008-2014) versus post- (2014-2021) KAS/ACA using chi-square tests. Next, we performed a competing risk analysis to study the effect of private versus public (Medicare, Medicaid, or government-sponsored) insurance on waitlist outcomes and a Cox survival analysis to study posttransplant outcomes while controlling for candidate, and recipient and donor variables, respectively.

Results

The proportion of overall KT candidates insured by Medicaid increased from pre-KAS/ACA to post-KAS/ACA (from 12 667 [7.3%] to 21 768 [8.8%], P < 0.0001). However, KT candidates with public insurance were more likely to have died or become too sick for KT (subdistribution hazard ratio [SHR] = 1.33, confidence interval [CI], 1.30-1.36) or to receive a deceased donor KT (SHR = 1.57, CI, 1.54-1.60) but less likely to receive a living donor KT (SHR = 0.87, CI, 0.85-0.89). Post-KT, KT recipients with public insurance had greater risk of mortality (relative risks = 1.22, CI, 1.15-1.31) and allograft failure (relative risks = 1.10, CI, 1.03-1.29).

Conclusions

Although the implementation of ACA marginally increased the proportion of waitlisted candidates with Medicaid, publicly insured KT candidates remained at greater risk of being removed from the waitlist, had lower probability of living donor kidney transplantation, and had greater probability of dying post-KT and allograft failure. Concerted efforts to address factors contributing to these inequities in future studies are needed, with the goal of achieving equity in KT for all.

Waiting-List and early posttransplant prognosis among ethnoracial groups: Data from the organ procurement and transplantation network

Background

Racial/ethnic disparity in waiting-list mortality among candidates listed for kidney transplantation (KT) in the United States remains unclear. We aimed to assess racial/ethnic disparity in waiting-list prognosis among patients listed for KT in the United States in the current era.

Methods

We compared waiting-list and early posttransplant in-hospital mortality or primary nonfunction (PNF) among adult (age ≥18 years) white, black, Hispanic, and Asian patients listed for only KT in the United States between July 1, 2004 and March 31, 2020.

Results

Of the 516,451 participants, 45.6%, 29.8%, 17.5%, and 7.1% were white, black, Hispanic, and Asian, respectively. Mortality on the 3-year waiting list (including patients who were removed for deterioration) was 23.2%, 16.6%, 16.2%, and 13.8% in white, black, Hispanic, and Asian patients, respectively. The cumulative incidence of posttransplant in-hospital death or PNF after KT was 3.3%, 2.5%, 2.4%, and 2.2% in black, white, Hispanic, and Asian patients,respectively. White candidates had the highest mortality risk on the waiting list or of becoming too sick for a transplant, while black (adjusted hazard ratio, [95% confidence interval, CI], 0.67 [0.66-0.68]), Hispanic (0.59 [0.58-0.60]), and Asian (0.54 [0.52-0.55]) candidates had a lower risk. Black KT recipients (odds ratio, [95% CI] 1.29 [1.21-1.38]) had a higher risk of PNF or death before discharge than white patients. After controlling confounders, black recipients (0.99 [0.92-1.07]) had a similar higher risk of posttransplant in-hospital mortality or PNF as white patients than Hispanic and Asian counterparts.

Conclusions

Despite having a better socioeconomic status and being allocated better kidneys, white patients had the worst prognosis during the waiting periods. Black recipients and white recipients have higher posttransplant in-hospital mortality or PNF.

Early Effect of the Circular Model of Kidney Allocation in the United States

BACKGROUND

In March 2021, the United States implemented a new kidney allocation system (KAS250) for deceased donor kidney transplantation (DDKT), which eliminated the donation service area-based allocation and replaced it with a system on the basis of distance from donor hospital to transplant center within/outside a radius of 250 nautical miles. The effect of this policy on kidney discards and logistics is unknown.

METHODS

We examined discards, donor-recipient characteristics, cold ischemia time (CIT), and delayed graft function (DGF) during the first 9 months of KAS250 compared with a pre-KAS250 cohort from the preceding 2 years. Changes in discards and CIT after the onset of COVID-19 and the implementation of KAS250 were evaluated using an interrupted time-series model. Changes in allocation practices (biopsy, machine perfusion, and virtual cross-match) were also evaluated.

RESULTS

Post-KAS250 saw a two-fold increase in kidneys imported from nonlocal organ procurement organizations (OPO) and a higher proportion of recipients with calculated panel reactive antibody (cPRA) 81%-98% (12% versus 8%; P <0.001) and those with >5 years of pretransplant dialysis (35% versus 33%; P <0.001). CIT increased (mean 2 hours), including among local OPO kidneys. DGF was similar on adjusted analysis. Discards after KAS250 did not immediately change, but we observed a statistically significant increase over time that was independent of donor quality. Machine perfusion use decreased, whereas reliance on virtual cross-match increased, which was associated with shorter CIT.

CONCLUSIONS

Early trends after KAS250 show an increase in transplant access to patients with cPRA>80% and those with longer dialysis duration, but this was accompanied by an increase in CIT and a suggestion of worsening kidney discards.

Improving equity in kidney transplant allocation policies through a novel genetic metric: The Matched Donor Potential

The demand for donors' kidneys continues to increase amid a shortage of available donors. Managing policies to thoughtfully allocate this scarce resource is a complex process. Although human leukocyte antigen (HLA) matching has been shown to prolong graft survival, its relative contribution to allocation schemes is empirically compromised owing to competing priorities. We explored using a new metric, Matched Donor Potential (MDP), to facilitate improved HLA matching while promoting equity. We interrogated all active kidney waitlist patients (N = 164 427), their corresponding unacceptable antigen files, and all effective donors in the Scientific Registry of Transplant Recipients (January 1, 2016-December 31, 2017). Cause-specific hazard functions were evaluated to assess the potential impact of the MDP metric on deceased donor transplant access rates for all candidates. Access was affected by ethnicity, blood group type, and calculated Panel Reactive Antibody (cPRA). Importantly, we show that access to transplantation is influenced by the patient's own HLA makeup regardless of their ethnicity and by the HLA makeup of effective donors. The MDP metric demonstrates a high association with access to transplantation. Adjusting Cox models to include this new metric resulted in improved access to kidney transplantation for waitlist candidates of minority heritage while significantly promoting HLA matching. Thus, the MDP metric accounts for balanced, equitable organ allocation algorithms.

Clinical Phenotypes of Dual Kidney Transplant Recipients in the United States as Identified through Machine Learning Consensus Clustering

Background and Objectives: Our study aimed to cluster dual kidney transplant recipients using an unsupervised machine learning approach to characterize donors and recipients better and to compare the survival outcomes across these various clusters. Materials and Methods: We performed consensus cluster analysis based on recipient-, donor-, and transplant-related characteristics in 2821 dual kidney transplant recipients from 2010 to 2019 in the OPTN/UNOS database. We determined the important characteristics of each assigned cluster and compared the post-transplant outcomes between clusters. Results: Two clinically distinct clusters were identified by consensus cluster analysis. Cluster 1 patients was characterized by younger patients (mean recipient age 49 ± 13 years) who received dual kidney transplant from pediatric (mean donor age 3 ± 8 years) non-expanded criteria deceased donor (100% non-ECD). In contrast, Cluster 2 patients were characterized by older patients (mean recipient age 63 ± 9 years) who received dual kidney transplant from adult (mean donor age 59 ± 11 years) donor with high kidney donor profile index (KDPI) score (59% had KDPI ≥ 85). Cluster 1 had higher patient survival (98.0% vs. 94.6% at 1 year, and 92.1% vs. 76.3% at 5 years), and lower acute rejection (4.2% vs. 6.1% within 1 year), when compared to cluster 2. Death-censored graft survival was comparable between two groups (93.5% vs. 94.9% at 1 year, and 89.2% vs. 84.8% at 5 years). Conclusions: In summary, DKT in the United States remains uncommon. Two clusters, based on specific recipient and donor characteristics, were identified through an unsupervised machine learning approach. Despite varying differences in donor and recipient age between the two clusters, death-censored graft survival was excellent and comparable. Broader utilization of DKT from high KDPI kidneys and pediatric en bloc kidneys should be encouraged to better address the ongoing organ shortage.

Kidney utility and futility

Changes in kidney allocation coupled with the COVID-19 pandemic have placed tremendous strain on current systems of organ distribution and logistics. Although the number of deceased donors continues to rise annually in the United States, the proportion of marginal deceased donors (MDDs) is disproportionately growing. Cold ischemia times and kidney discard rates are rising in part related to inadequate planning, resources, and shortages. Complexity in kidney allocation and distribution has contributed to this dilemma. Logistical issues and the ability to reperfuse the kidney within acceptable time constraints increasingly determine clinical decision-making for organ acceptance. We have a good understanding of the phenotype of "hard to place" MDD kidneys, yet continue to promote a "one size fits all" approach to organ allocation. Allocation and transportation systems need to be agile, mobile, and flexible in order to accommodate the expanding numbers of MDD organs. By identifying "hard to place" MDD kidneys early and implementing a "fast-track" or open offer policy to expedite placement, the utilization rate of MDDs would improve dramatically. Organ allocation and distribution based on location, motivation, and innovation must lead the way. In the absence of change, we are sacrificing utility for futility and discard rates will continue to escalate.

The new French kidney allocation system for donations after brain death: Rationale, implementation, and evaluation

In recent decades, the allocation policies of many countries have moved from center-based to patient-based approaches. The new French kidney allocation system (KAS) of donations after brain death for adult recipients, implemented in 2015, was principally designed to introduce a unified allocation score (UAS) to be applied locally for one kidney and nationally for the other and to replace regional borders by a new geographical model. The new KAS balances dialysis duration and waiting time to compensate for listing delays and provides more effective longevity matching between donors and recipients with better HLA and age matching. We report these changes, with their rationale and main results. Results show improved HLA matching for young recipients and more rapid access to transplant for older recipients. Young recipients also had better access to transplantation. Transplant access decreased for recipients aged 60-69 and required tuning of KAS parameters. In conclusion, our results strongly indicate that national or adequately broad geographic allocation areas, combined with multiplicative interactions between allocation criteria, permit multivariate optimization of organ allocation and thus improve national kidney sharing and balance HLA matching and age matching, at the price of longer cold ischemic times and more logistical constraints than with local allocation.

Geographic hot spots of kidney transplant candidates wait-listed post-dialysis

INTRODUCTION

Preemptive wait-listing of deceased donor kidney transplant (DDKT) candidates before maintenance dialysis increases the likelihood of transplantation and improves outcomes among transplant patients. Previous studies have identified substantial disparities in rates of preemptive listing, but a gap exists in examining geographic sources of disparities, particularly for sub-regional units. Identifying small area hot spots where delayed listing is particularly prevalent may more effectively inform both health policy and regionally appropriate interventions.

METHODS

We conducted a retrospective cohort study utilizing 2010-2020 Scientific Registry of Transplant Recipients (SRTR) data for all DDKT candidates to examine overall and race-stratified geospatial hot spots of post-dialysis wait-listing in U.S. zip code tabulation areas (ZCTA). Three geographic clustering methods were utilized to identify robust statistically significant hot spots of post-dialysis wait-listing.

RESULTS

Novel sub-regional hot spots were identified in the southeast, southwest, Appalachia, and California, with a majority existing in the southeast. Race-stratified results were more nuanced, but broadly reflected similar patterns. Comparing transplant candidates in hot spots to candidates in non-clusters indicated a strong association between residence in hot spots and high area deprivation (OR: 6.76, 95%CI: 6.52-7.02), indicating that improving access healthcare in these areas may be particularly beneficial.

CONCLUSION

Our study identified overall and race-stratified hot spots with low rates of preemptive wait list placement in the U.S., which may be useful for prospective healthcare policy and interventions via targeting of these narrowly defined geographical areas.

Scandiatransplant acceptable mismatch program-10 years with an effective strategy for transplanting highly sensitized patients

In March 2009, the Scandiatransplant acceptable mismatch program (STAMP) was introduced as a strategy toward improving kidney allocation to highly sensitized patients. Patients with a transplantability score ≤ 2% are potential candidates for the program. Samples are analyzed and acceptable antigens (HLA-A, B, C, DRB1, DRB3/4/5, DQB1, DQA1, DPB1, DPA1) are defined by the local tissue typing laboratory and finally evaluated by a steering committee. In the matching algorithm, patients have the highest priority when the donor's antigens are all among the recipient's own or acceptable HLA antigens. In the period from 2009 to 2020, we have transplanted 278 highly sensitized kidney patients through the program. The graft survival of the STAMP patients was compared with 9002 deceased donor kidney-transplanted patients, transplanted in the same time period. The 10-year graft survival was 73.4% (95% CI: 60.3-90.0) for STAMP and 82.9% (95% CI: 81.6-84.3) for the reference group. (p = .2). In conclusion, the 10-year allograft survival demonstrates that the STAMP allocation algorithm is immunological safe. The program is continuously monitored and evaluated, and the introduction of matching for all HLA loci is a huge improvement to the program and demonstrate technical adaptability as well as clinical flexibility in a de-centralized organization.

ABO-adjusted calculated panel reactive antibody (cPRA): A unified metric for immunologic compatibility in kidney transplantation

Implementation of the kidney allocation system in 2014 greatly reduced access disparity due to human leukocyte antigen (HLA) sensitization. To address persistent disparity related to candidate ABO blood groups, herein we propose a novel metric termed "ABO-adjusted cPRA," which simultaneously considers the impact of candidate HLA and ABO sensitization on the same scale. An ethnic-weighted ABO-adjusted cPRA value was computed for 190 467 candidates on the kidney waitlist by combining candidate's conventional HLA cPRA with the remaining fraction of HLA-compatible donors that are ABO-incompatible. Consideration of ABO sensitization resulted in higher ABO-adjusted cPRA relative to conventional cPRA by HLA alone, except for AB candidates since they are not ABO-sensitized. Within cPRA Point Group = 99%, 43% of the candidates moved up to ABO-adjusted cPRA Point Group = 100%, though this proportion varied substantially by candidate blood group. Nearly all O and most B candidates would have elevated ABO-adjusted cPRA values above this policy threshold for allocation priority, but relatively few A candidates displayed this shift. Overall, ABO-adjusted cPRA more accurately measures the proportion of immune-compatible donors compared with conventional HLA cPRA, especially for highly sensitized candidates. Implementation of this novel metric could enable the development of allocation policies permitting more ABO-compatible transplants without compromising equity.

The New Distance-Based Kidney Allocation System: Implications for Patients, Transplant Centers, and Organ Procurement Organizations

Purpose of Review

The goal of deceased donor kidney allocation policy is to provide objective prioritization for donated kidneys, and policy has undergone a series of revisions in the past decade in attempt to achieve equity and utility in access to kidney transplantation. Most recently, to address geographic disparities in access to kidney transplantation, the Kidney Allocation System changed to a distance-based allocation system—colloquially termed “KAS 250”—moving away from donor service areas as the geographic basis of allocation. We review the early impact of this policy change on access to transplant for patients, and on complexity of organ allocation and transplantation for transplant centers and organ procurement organizations.

Recent Findings

Broader sharing of kidneys has increased complexity of the allocation system, as transplant centers and OPOs now interact in larger networks. The increased competition resulting from this system, and the increased operational burden on centers and OPOs resulting from greater numbers of organ offers, may adversely affect organ utilization. Preliminary results suggest an increase in transplant rate overall but a trend toward higher kidney discard and increased cold ischemia time.

Summary

The KAS 250 allocation policy changed the geographic basis of deceased donor kidney distribution in a manner that is intended to reduce geographic disparities in access to kidney transplantation. Close monitoring of this policy’s impact on patients, transplant center behavior, and process measures is critical to the aim of maximizing access to transplant while achieving transplant equity.