Beyond donation to organ utilization in the USA

The Survival Benefit of Accepting an Older Donor Lung Transplant Compared With Waiting for a Younger Donor Offer

BACKGROUND

Donor pool expansion is critical as lung candidates suffer high mortality, yet older donor lungs remain underutilized. We evaluated whether accepting an older donor (defined 4 ways: donor age 30-39, 40-49, 50-59, or 60-69 y) lung transplant was associated with a survival benefit over waiting for a younger donor offer.

METHODS

Adult candidates who received a lung offer were identified using Scientific Registry of Transplant Recipients data, 2015-2022. Offers were categorized by donor age and candidate lung allocation score (LAS; <40, 40-55, >55). Postoffer mortality was compared between candidates for whom the offer was accepted ("acceptors") versus declined ("decliners") within each age-LAS category using weighted Cox regression.

RESULTS

A total of 21 426 candidates received an offer from a donor age ≥30 y; 11 679 accepted. For LAS >55 candidates, a survival benefit was observed for acceptors of donors ages 30-39 y (weighted hazard ratio [wHR] of mortality: 0.450.520.59), 40-49 y (wHR: 0.610.700.79), and 50-59 y (wHR: 0.670.770.88); P < 0.001. For candidates with LAS 40-55, results suggest a survival benefit of accepting lung offers from donors age 30-39 y (wHR: 0.770.870.99) and 40-49 y (wHR: 0.760.870.99); P = 0.03. However, for candidates with LAS <40, a survival benefit was not observed for accepting any older donor transplant, with possible harm in accepting an age 50+ donor offer.

CONCLUSIONS

Compared with declining and waiting for a younger donor offer, accepting an older donor lung transplant was associated with a survival advantage in candidates with high LAS in the precontinuous distribution era. Decision makers should consider these findings while recognizing potential changes in waiting time dynamics in the current era.

Optimizing kidney allocation: challenges and solutions

PURPOSE OF REVIEW

With the kidney nonuse rate approaching 30%, one-fifth of kidneys placed out of sequence, and unsatisfactory long-term recipient outcomes, U.S. kidney allocation is at a crossroads. This review highlights recent studies and efforts geared toward improving the system.

RECENT FINDINGS

The Organ Procurement & Transplantation Network's kidney transplantation committee is tasked with migrating kidney allocation policy, currently based on 250 nautical mile circles, to a fully continuous, points-based system. Challenges in designing a system assured to improve, not worsen, placement efficiency have hampered progress. OPO and transplant center practice patterns have adapted to a rapidly changing donation landscape. Advances in transplant immunology, particularly involving molecular HLA typing methods, are opening doors for more precise donor-recipient matching that appear to hold promise for improved long-term outcomes.

SUMMARY

The largely one-size-fits-all kidney allocation system is in desperate need of an overhaul. The continuous distribution paradigm is flexible enough to accommodate bold, new ideas for addressing major pain points in an equitable way. The OPTN should use policy variances to conduct time-limited, controlled experiments with various continuous distribution policies and build upon what works. Advances in transplant immunology, such as eplet matching, should increasingly be incorporated into kidney offer decision-making and, eventually, the allocation algorithm.

Partial Heart Transplantation Promotes Organ Stewardship: Domino Hearts and Split Roots

Background

Partial heart transplantation (PHT) has emerged as a pioneering approach for treating infants with irreparable heart valve dysfunction. However, the scarcity of suitable donors presents a significant bottleneck to its widespread application. This study introduces and evaluates the novel use of domino and split-root procedures within PHT.

Methods

We describe 6 pediatric cardiac patients who underwent either domino or split-root PHT at our institution.

Results

From May to August 2023, our team successfully executed 3 domino and 3 split-root PHTs, including 1 procedure that involved interinstitutional collaboration. These cases highlight the procedural feasibility and the potential for broader application.

Conclusions

The implementation of PHT represents a significant advance in pediatric heart care. Domino and split-root techniques within the PHT framework have the potential to substantially increase both donor availability and recipient capacity. These strategies usher in a new era of organ stewardship through addressing the challenge of donor organ shortage.

Cardiac transplantation with increased-risk donors: Trends and clinical outcomes

BACKGROUND

Orthotopic Heart transplantation (OHT) is a definitive treatment for patients with advanced heart failure. Despite available evidence, recipients and some clinicians remain hesitant to accept organs from Increased Risk Donors (IRD). This study aims to report trends in acceptance of donors from IRD donors and long-term outcomes.

METHODS

This study is an analysis of OHT recipients captured in the United Network of Organ Sharing (UNOS) registry from 2004 to 2021. OHT recipients were dichotomized by IRD status. Primary objectives were to report survival following OHT and trends in IRD use. Secondary objectives included all-cause hospitalizations, hospitalizations for infection, treated rejection, and graft failure.

RESULTS

Of the 36,989 OHT recipients within the study period, 7779 (21%) were identified as recipients of IRD. Recipients of IRD were older (57 years vs 56 years, p ≤0.001), more likely to be African American (23% vs 21%, p = 0.006), blood group O (40% vs 38%, p = 0.02), have public insurance (52% vs 50%, p = 0.02), and have a BMI >30 (30% vs 29%, p = 0.003). IRD recipients had shorter waitlist time (69 days vs 76 days, p = 0.009) and similar long-term survival. IRD recipients also had lower odds of rehospitalization due to infection (OR 0.893, CI 0.842-0.947; p = 0.0002) and lower odds of rehospitalization due to rejection (OR 0.849, CI 0.782-0.921; p ≤0.001).

CONCLUSIONS

In this large multicenter study, we report that recipients of IRD had similar long-term survival and incidence of graft failure as recipients of standard risk donors. Further analysis is needed to understand observed differences in outcomes of hospitalizations for infection and treated rejection.

Does a changing donor pool explain the recent rise in the United States kidney nonuse rate?

The proportion of deceased donor kidneys recovered for transplantation that are not transplanted reached 28% in 2023. Past research demonstrated that >90% of the nonuse rate (NUR) increase in the 2000s could be explained by the broadening donor pool. We used the Organ Procurement and Transplantation Network data to study kidneys recovered from 2010-2023, applying causal inference methods to assess the degree to which the recent, sharp rise in the NUR could be explained by changes in donor clinical characteristics. Unadjusted odds of kidney nonuse were 63% higher (95% CI: 56%, 70%) in 2023 vs 2018. After adjusting for donor factors, the odds of nonuse were only 12% (9%, 15%) higher in 2023. Both regression and propensity weighting demonstrated that 75% to 80% of the recent NUR increase can be explained by a rapidly expanding donor pool. Encouragingly, the NUR has not increased and remains low for above-average quality kidneys. However, the unexplained risk of nonuse for kidneys in the highest kidney donor risk index quartile increased by ∼ 30%, potentially due to residual confounding and/or system-level, exogenous factors such as allocation policy changes. To improve placement efficiency, allocation policy should adapt to the increasingly heterogeneous donor pool by allocating kidneys differently along the donor quality spectrum.

Crossing national borders for transplantation: A focused evaluation of deceased donor lung exports from the United States

Organ transplantation is a life-saving treatment for end-stage organ failure patients, but the United States (US) faces a shortage of available organs. US policies incentivize identifying recipients for all recovered organs. Technological advancements have extended donor organ viability, creating new opportunities for long-distance transport and international sharing. We aimed to assess organ exports from deceased US donors to candidates abroad, a component of allocation policy allowed without suitable domestic candidates. Based on the national Scientific Registry of Transplant Recipients data from January 2014 to September 2023, 388 342 organs were recovered for transplantation, with 511 (0.13%) exported. Most exported organs were lungs (80%). Exported lung donors were older (41 vs 34 years, P < .001), more likely hepatitis C positive (22% vs 4%, P < .001), and more likely donors after circulatory death (20% vs 7%, P < .001). Lungs that were eventually exported were offered to more US potential transplant recipients (median = 65) than those kept in the US (median = 21 and 41 for lungs recovered by nonexporting and exporting organ procurement organizations, respectively; P < .001). Our study highlights the necessity for further research and clear policy initiatives to balance the benefits of cross-border sharing while considering potential opportunities for more aggressive organ allocation within the US.

Donor MHC-specific thymus vaccination allows for immunocompatible allotransplantation

Organ transplantation is the last-resort option to treat organ failure. However, less than 10% of patients benefit from this only option due to lack of major histocompatibility complex (MHC)-matched donor organs and 25%-80% of donated organs could not find MHC-matched recipients. T cell allorecognition is the principal mechanism for allogeneic graft rejection. We herein present a "donor MHC-specific thymus vaccination" (DMTV) strategy to induce T cell tolerance to both autologous and allogeneic donor MHC. Allogeneic MHC molecules were expressed in the recipient thymus through adeno-associated virus-mediated delivery, which led to stable expression of allogeneic MHC together with the autologous MHC in the engineered thymus. During local T cell education, those T cells recognizing either autologous MHC or allogeneic MHC were equally depleted. We constructed C57BL/6-MHC and BALB/c-MHC dual immunocompatible mice via thymus vaccination of C57BL/6-MHC into the BALB/c thymus and observed long-term graft tolerance after transplantation of C57BL/6 skin and C57BL/6 mouse embryonic stem cells into the vaccinated BALB/c mice. We also validated our DMTV strategy in a bone marrow, liver, thymus (BLT)-humanized mouse model for immunocompatible allotransplantation of human embryonic stem cells. Our study suggests that the DMTV strategy is a potent avenue to introduce a donor compatible immune system in recipients, which overcomes the clinical dilemma of the extreme shortage of MHC-matched donor organs for treating patients with end-stage organ failure.

The dynamics of deceased donor kidney transplant decision making: insights from studying individual clinicians' offer decisions

Despite the high demand, >7500 recovered kidneys annually go unused, with transplant centers showing significant variation in their offer acceptance practices. However, it remains unclear how much of this variation occurs between individual clinicians within the same center and its impact on allocation efficiency and equity. This study quantified the variability in kidney offer acceptance decisions attributable to clinicians vs centers and examined the role of donor quality in acceptance decisions. We analyzed national transplant registry data (from January 2016 to December 2020) linked to on-call records from 15 transplant centers, creating a clinician-level data set with 344 678 deceased donor kidney offers. The primary outcome was the variability in offer acceptance attributable to clinicians vs centers, quantified via hierarchical, mixed-effect logistic regression models. To complement kidney donor profile index as a measure of donor quality, we incorporated expected acceptance probability, adjusting for a broader set of donor characteristics and recipient factors. Both center-level (0.35; 95% CI: 0.15-0.79) and clinician-level (0.10; 95% CI: 0.06-0.18) variances were significant, with heterogeneity in the kidney donor profile index-acceptance association among clinicians. These results underscore the need for further research into the mechanisms driving the clinician-level variation and its implications for organ allocation efficacy, equity, and patient outcomes.

The Centennial Allograft: Cumulative Kidney and Liver Function for More Than 100 Years

The maximum cumulative life span of kidneys and livers first in donors and then in transplant recipients has not been established. The purpose of this study was to determine if cumulative organ function for more than 90 years is possible for transplanted kidneys and livers. This study included kidney and liver transplants from living or deceased donors ≥55 years. Cumulative organ function (COF) = Organ Age at Donation [Years] + Tx Allograft Function [Years]. Univariate and multivariable methods were used to describe characteristics and outcomes. Between 1987 and 2022, a total of 81,807 kidney and 37,099 liver transplants were included in this study. Of all kidney grafts 2.7% but 16.6% of all liver grafts reached the 90-year COF mark. There were only 2 living donor kidneys that surpassed the 100-year mark versus 29 deceased liver grafts. The longest kidney function was 104 years and longest liver function 108 years. Multivariate analysis showed that optimal donor and recipient selection and management are predictors for allograft longevity. COF in organs exceeding 100 physiologic years is possible. Extended organ longevity was 5 times more common for livers than kidneys. These analyses support that age alone should not exclude older kidney and liver donors from consideration for transplantation.

Understanding the dynamics of deceased organ donation and utilization in Colombia

Objective

To obtain a comprehensive overview of organ donation, organ utilization, and discard in the entire donation process in Colombia.

Methods

A retrospective study of 1 451 possible donors, distributed in three regions of Colombia, evaluated in 2022. The general characteristics, diagnosis, and causes of contraindication for potential donors were described.

Results

Among the 1 451 possible donors, 441 (30.4%) fulfilled brain death criteria, constituting the potential donor pool. Families consented to organ donation in 141 medically suitable cases, while 60 instances utilized legal presumption, leading to 201 eligible donors (13.9%). Of those, 160 (11.0%) were actual donors (in whom operative incision was made with the intent of organ recovery or who had at least one organ recovered). Finally, we identified 147 utilized donors (10.1%) (from whom at least one organ was transplanted). Statistically significant differences were found between age, sex, diagnosis of brain death, and donor critical pathway between regions. A total of 411 organs were transplanted from 147 utilized donors, with kidneys being the most frequently procured and transplanted organs, accounting for 280 (68.1%) of the total. This was followed by 85 livers (20.7%), 31 hearts (7.5%), 14 lungs (3.4%), and 1 pancreas (0.2%). The discard rate of procured deceased donors was 8.1%.

Conclusions

About one-tenth of donors are effectively used for transplantation purposes. Our findings highlight areas of success and challenges, providing a basis for future improvements in Colombia.