Perspectives on the Strengths and Weaknesses of the National Kidney Allocation System

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.

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

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Long-term outcomes of kidney transplantation from expanded criteria donors with Chinese novel donation policy: donation after citizens' death

Introduction

The Chinese Government initiated the Donation after Citizens' Death policy in 2010. To now, it has been a major source of organs for transplant. Since it is still a young policy, corresponding clinical evidence is still urgently needed for its improvement. Compared to kidneys donated by SCD (standard criteria donor), increasing the use of ECD (expanded criteria donor) derived kidneys is a way to expand the donor pool but is also a result of the aging demography of China. This study is based on the data of kidney transplantation in our center with the Donation after Citizens' Death policy, aiming to provide a reference for the clinical use of ECD kidneys.

Method

A retrospective study enrolled 415 kidney transplants derived from 211 donors performed between October 2011 and October 2019. A total of 311 (74.9%) organs were donated from 159 (75.4%) SCDs, and the remaining 104 (25.1%) were from 52 (24.6%) ECDs. The log-rank test was used to compare the difference in survival and postoperative complications. The Chi-square test was used to compare the occurrence of postoperative complications and postoperative renal function. The Cox regression analysis was used for risk factor screening.

Result

Analysis showed that grafts from ECD were poorer in survival (P = 0.013), while their recipients had comparable (P = 0.16) survival. Moreover, it also was an independent risk factor for graft loss (HR 2.27, P = 0.044). There were significantly more AR occurrences in the ECD group compared with SCD group (25.0% vs. 15.8%, P = 0.004), but no significant difference was found in infection (51.9% vs. 47.6%, P = 0.497) and DGF (26.0% vs. 21.9%, P = 0.419) between them. Similarly, fewer recipients in the ECD group were free from AR within 1 year after transplantation (P = 0.040), with no statistical difference in all-cause infection prevalence in 1 year (P = 0.168). The eGFR in the ECD group was significantly worse than that in the SCD group at 3 months, 6 months, 1 year, 3 years, and the highest value posttransplant (all < 0.05), but no difference at 5 years posttransplant. Besides, results showed cardiac arrest (uncontrolled vs. controlled, HR 2.49, P = 0.049), HLA mismatch (4–6 loci vs. 0–3 loci, HR 3.61, P = 0.039), and AR occurrence (HR 2.91, P = 0.006) were demonstrated to be independent risk factors for graft loss.

Conclusion

The ECD-derived kidney was worse than the SCD-derived kidney in terms of graft survival and AR occurrence, and trend to an inferior renal function postoperative. However, the recipient survival, DGF occurrence, and all-cause infection occurrence were similar.

A tool for decision-making in kidney transplant candidates with poor prognosis to receive deceased donor transplantation in the United States

The primary outcomes for kidney transplant candidates are receipt of deceased or living donor transplant, death or removal from the waiting list. Here, we conducted a retrospective analysis of national Scientific Registry of Transplant Recipients data to evaluate outcomes for 208,717 adult kidney transplant candidates following the 2014 Kidney Allocation System in the United States. Competing risks models were utilized to evaluate Time to Equivalent Risk (TiTER) of deceased donor transplantation (DDTX) and death versus waitlist removal. We also evaluated TiTER based on kidney donor profile index (KDPI) and donor age. For all groups, the cumulative incidence of DDTX was initially higher from time of listing than death or waitlist removal. However, following accrued time on the waiting list, the cumulative incidence of death or waitlist removal exceeded DDTX for certain patient groups, particularly older, diabetic, blood type B and O and shorter pre-listing dialysis time. TiTER for all candidates aged 65-69 averaged 41 months and for 70 and older patients 28 months. Overall, 39.6% of candidates were in risk groups with TiTER under 72 months and 18.5% in groups with TiTER under 24 months. Particularly for older candidates, TiTER for kidneys was substantially shorter for younger donors or lower KDPI. Thus, our findings reveal that a large proportion of waitlisted patients in the United States have poor prognoses to ever undergo DDTX and our data may improve shared decision-making for candidates at time of waitlist placement. Hence, for specific patient groups, TiTER may be a useful tool to disseminate and quantify benefits of accepting relatively high risk donor organs.

Patients with High Priority for Kidney Transplant Who Are Not Given Expedited Placement on the Transplant Waiting List Represent Lost Opportunities

BACKGROUND

Kidney transplantation is associated with the best outcomes for most patients with ESKD. The national Kidney Allocation System prioritizes patients with Estimated Post-Transplant Survival (EPTS) scores in the top 20% for expedited access to optimal deceased donor kidneys.

METHODS

We studied adults aged ≥18 years in the United States Renal Data System with top 20% EPTS scores who had been preemptively waitlisted or initiated dialysis in 2015-2017. We evaluated time to waitlist placement, transplantation, and mortality with unadjusted and multivariable survival models.

RESULTS

Of 42,445 patients with top 20% EPTS scores (mean age, 38.0 years; 57% male; 59% White patients, and 31% Black patients), 7922 were preemptively waitlisted. Among 34,523 patients initiating dialysis, the 3-year cumulative waitlist placement incidence was 37%. Numerous factors independently associated with waitlisting included race, income, and having noncommercial insurance. For example, waitlisting was less likely for Black versus White patients, and for patients in the lowest-income neighborhoods versus those in the highest-income neighborhoods. Among patients initiating dialysis, 61% lost their top 20% EPTS status within 30 months versus 18% of patients who were preemptively listed. The 3-year incidence of deceased and living donor transplantation was 5% and 6%, respectively, for patients who initiated dialysis and 26% and 44%, respectively, for patients who were preemptively listed.

CONCLUSIONS

Many patients with ESKDqualifying with top 20% EPTS status are not placed on the transplant waiting list in a timely manner, with significant variation on the basis of demographic and social factors. Patients who are preemptively listed are more likely to receive benefits of top 20% EPTS status. Efforts to expedite care for qualifying candidates are needed, and automated transplant referral for patients with the best prognoses should be considered.

PODCAST

This article contains a podcast athttps://www.asn-online.org/media/podcast/JASN/2021_07_30_JASN2020081146.mp3.

Failure to Advance Access to Kidney Transplantation over Two Decades in the United States

BACKGROUND

Extensive research and policies have been developed to improve access to kidney transplantation among patients with ESKD. Despite this, wide variation in transplant referral rates exists between dialysis facilities.

METHODS

To evaluate the longitudinal pattern of access to kidney transplantation over the past two decades, we conducted a retrospective cohort study of adult patients with ESKD initiating ESKD or placed on a transplant waiting list from 1997 to 2016 in the United States Renal Data System. We used cumulative incidence models accounting for competing risks and multivariable Cox models to evaluate time to waiting list placement or transplantation (WLT) from ESKD onset.

RESULTS

Among the study population of 1,309,998 adult patients, cumulative 4-year WLT was 29.7%, which was unchanged over five eras. Preemptive WLT (prior to dialysis) increased by era (5.2% in 1997-2000 to 9.8% in 2013-2016), as did 4-year WLT incidence among patients aged 60-70 (13.4% in 1997-2000 to 19.8% in 2013-2016). Four-year WLT incidence diminished among patients aged 18-39 (55.8%-48.8%). Incidence of WLT was substantially lower among patients in lower-income communities, with no improvement over time. Likelihood of WLT after dialysis significantly declined over time (adjusted hazard ratio, 0.80; 95% confidence interval, 0.79 to 0.82) in 2013-2016 relative to 1997-2000.

CONCLUSIONS

Despite wide recognition, policy reforms, and extensive research, rates of WLT following ESKD onset did not seem to improve in more than two decades and were consistently reduced among vulnerable populations. Improving access to transplantation may require more substantial interventions.

Modest rates and wide variation in timely access to repeat kidney transplantation in the United States

Success of transplantation is not limited to initial receipt of a donor organ. Many kidney transplant recipients experience graft loss following initial transplantation and the benefits of expedited placement on the waiting list and retransplantation extend to this population. Factors associated with access to repeat transplantation may be unique given experience with the transplant process and prior viability as a candidate. We examined the incidence, risk factors, secular changes, and center-level variation of preemptive relisting or transplantation (PRLT) for kidney transplant recipients in the United States with graft failure (not due to death) using Scientific Registry of Transplant Recipients data from 2007 to 2018 (n = 39 557). Overall incidence of PRLT was 15% and rates of relisting declined over time. Significantly lower PRLT was evident among patients who were African American and Hispanic, males, older, obese, publicly insured, had lower educational attainment, were diabetic, had longer dialysis time prior to initial transplant, shorter graft survival, longer distance to transplant center, and resided in distressed communities. There was significant variation in PRLT by center, median = 13%, 10th percentile = 6%, 90th percentile = 24%. Cumulatively, results indicate that despite prior access to transplantation, incidence of PRLT is modest with pronounced clinical, social, and center-level sources of variation suggesting opportunities to improve preemptive care among patients with failing grafts.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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