The new allocation era and policy

Early outcomes of lung transplantation under the composite allocation score system

PURPOSE

The Composite Allocation Score was introduced in March 2023 with the goal of improving organ allocation for potential lung transplant recipients. The purpose of this study is to characterize waitlist and post-transplant outcomes for adult lung transplant recipients under the Composite Allocation Score policy.

METHODS

We included all adult candidates listed for isolated lung transplantation in the United States from May 2022 to December 2023. Candidates were categorized into 2 eras: Era 1 (pre-Composite Allocation Score, May 15, 2022 to March 8, 2023) and Era 2 (post--Composite Allocation Score, March 9, 2023 to December 31, 2023). Waitlist mortality and transplant rates within 9 months of listing were compared using competing risk regression. Post-transplant outcomes of the 2 groups were also compared. Kaplan-Meier was used to evaluate 9-month survival post-transplant.

RESULTS

A total of 5293 candidates were listed, with 2744 (51.8%) during Era 2. Lung transplant candidates in Era 2 experienced lower waitlist mortality (sub-hazard ratio, 0.79; 95% CI, 0.69-0.92, P = .002) and higher transplant rates (sub-hazard ratio, 1.22; 95% CI, 1.15-1.28, P < .001) compared with those in Era 1. Post-transplant extracorporeal membrane oxygenation rates at 72 hours (11.1% vs 9.9%, P = .25) and 30-day mortality (2.3% vs 2.4%, P = .96) were similar between Era 2 and Era 1. Nine-month survival after transplantation was not significantly different between Era 2 and Era 1 recipients (91.7% vs 90.9%, P = .47).

CONCLUSIONS

Lung transplant candidates in Era 2 had lower waitlist mortality and higher transplant rates compared with Era 1, with similar 9-month post-transplant survival. These findings suggest that the Composite Allocation Score policy has contributed to allocation improvement without compromising early post-transplant outcomes.

National Trends and Outcomes of Combined Lung-Liver Transplantation: An Analysis of the UNOS Registry

PURPOSE

Combined lung-liver transplant (CLLT) is a complex yet life-saving procedure for patients with simultaneous end-stage lung and liver disease. Given the geographical allocation change to the lung allocation score (LAS) in 2017 and the recent SARS-CoV-2 outbreak in 2019, we aim to provide an updated analysis of the patient selection and outcomes of CLLTs.

METHODS

The UNOS registry was used to identify all patients who underwent CLLT between January 2014 and June 2023. To account for the changes made to LAS in 2017, baseline characteristics and outcomes were compared between era 1 (before 2017) and era 2 (after 2017). Risk factors for mortality were analyzed using the Cox regression hazard models. Recipient survival of up to 3 years was analyzed using the Kaplan-Meier method.

RESULTS

117 CLLTs were performed (77.8% in era 2). Donor organs experienced significantly longer ischemic times (p = 0.039) and traveled longer distances (p = 0.025) in era 2. However, recipient (p = 0.79) and graft (p = 0.41) survival remained comparable at up to 3 years post-transplant between eras. CLLTs demonstrated similar long-term survival to isolated lung transplants (p = 0.73). Higher recipient LAS was associated with an increased mortality risk (HR 1.14, p = 0.034). Recipient diagnosis of idiopathic pulmonary fibrosis carried a 5.03-fold risk of mortality (p = 0.048) compared to those with cystic fibrosis.

CONCLUSION

In the post-2017 LAS change era, CLLTs are increasingly performed with comparable outcomes to isolated lung transplants. A careful, multidisciplinary approach to patient selection and management remains paramount to optimizing outcomes for this rare patient population.

Development of a Machine Learning-Powered Optimized Lung Allocation System for Maximum Benefits in Lung Transplantation: A Korean National Data

BACKGROUND

An ideal lung allocation system should reduce waiting list deaths, improve transplant survival, and ensure equitable organ allocation. This study aimed to develop a novel lung allocation score (LAS) system, the MaxBenefit LAS, to maximize transplant benefits.

METHODS

This study retrospectively analyzed data from the Korean Network for Organ Sharing database, including 1,599 lung transplant candidates between September 2009 and December 2020. We developed the MaxBenefit LAS, combining a waitlist mortality model and a post-transplant survival model using elastic-net Cox regression, was assessed using area under the curve (AUC) values and Uno's C-index. Its performance was compared to the US LAS in an independent cohort.

RESULTS

The waitlist mortality model showed strong predictive performance with AUC values of 0.834 and 0.818 in the training and validation cohorts, respectively. The post-transplant survival model also demonstrated good predictive ability (AUC: 0.708 and 0.685). The MaxBenefit LAS effectively stratified patients by risk, with higher scores correlating with increased waitlist mortality and decreased post-transplant mortality. The MaxBenefit LAS outperformed the conventional LAS in predicting waitlist death and identifying candidates with higher transplant benefits.

CONCLUSION

The MaxBenefit LAS offers a promising approach to optimizing lung allocation by balancing the urgency of candidates with their likelihood of survival post-transplant. This novel system has the potential to improve outcomes for lung transplant recipients and reduce waitlist mortality, providing a more equitable allocation of donor lungs.

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.

The association between pretransplant malignancy and post-transplant survival and cancer recurrence in bilateral lung transplantation: An analysis of 23,291 recipients

Background

Given the increasing need for lung transplants among older patients with a history of cancer, this study analyzed database registry to assess outcomes for bilateral lung transplant (BLT) recipients with pre-transplant malignancy (TM).

Methods

This study evaluated the United Network for Organ Sharing registry for adult BLT performed between 2005 and 2023. Patients with a history of previous or multiorgan transplants, and those with donors who had cancer history, were excluded. Propensity score matching was used to compare patients with or without pre-TM. Overall and post-TM-free survival were analyzed.

Results

Among the 23,291 recipients of BLT, 8.0% (1,870) had pre-TM. Compared to those without pre-TM, patients with pre-TM had worse overall (hazard ratio [HR] 1.20, 95% confidence interval [CI] 1.12-1.29, p < 0.001) and post-TM-free survival (HR 1.32, 95% CI 1.24-1.41, p < 0.001). However, after adjusting for age, sex, and race through propensity score matching, the survival difference between the groups became nonsignificant (HR 1.05, 95% CI 0.97-1.13, p = 0.229). While the pre-TM group still had worse post-TM-free survival, this difference diminished after excluding cutaneous post-TM (HR 1.06, 95% CI 0.99-1.15, p = 0.116). Additionally, the recurrence rate of pre-TM after transplant was not higher than de novo cancers in patients without pre-TM.

Conclusions

Patients with pre-TM had similar survival rates after BLT as those without pre-TM. Importantly, there was no increased risk of the primary pre-TM type recurring post-transplant compared to patients without pre-TM. If patients with pre-TM are free from recurrence or metastasis for a significant time, there could be some who can benefit from BLT. Further data regarding timeline between pre-TM and BLT would be necessary to draw conclusion in this issue.

Potential of new 250-nautical mile concentric circle allocation system for improving the donor/recipient HLA matching: Development of new matching algorithm

BACKGROUND

High-resolution typing of human leukocyte antigen (HLA) may revolutionize the field of kidney transplantation by selection of low immunogenic grafts. The new 250-nautical mile circle allocation system offers a unique opportunity to find low HLA immunogenic donors for eligible recipients.

METHODS

501 transplant candidates from the University of Toledo Medical Center (UTMC) between 2015 and 2019, registered at the Scientific Registry of Transplant Recipients (SRTR) were virtually matched to 4812 donors procured within 250-nautical miles using an in-house-developed simulation algorithm. Immunogenicity of HMS (hydrophobic mismatch score) ≤10 was measured based on imputed high-resolution HLAs. Simulated "optimal" matches with a KDPI≤50 % were compared with the transplant cohort between 2000 and 2010 with their kidney allograft survivals.

RESULTS

Out of 501 recipients 500 (99.8 %) were matched with donors ≤10 HMS and KDPI ≤50 %. The average HMS value for simulated transplants was 1.4 (range 0-10) versus 6.3 (range 0-75) in the retrospective cohort (p < 0.001). The simulated model had a median mismatch number of 3/6, while the reference cohort 4/6 among HLA-A/B/DR antigens (p < 0.001). The estimated median graft survival was 18.2 years for the simulated cohort vs. 13.4 years in the real-life cohort (p < 0.001), gaining 4.9 years per transplant and 2450 survival years for all patients. For year 2014, out of 98 patients and 659 donors, each recipient had a median number of 141 donors (HMS < 10; range 8-378). Similar values were found for patients between 2015 and 2019.

CONCLUSION

Donors within 250-nautical miles proffers excellent and multiple options for finding well-matched low immunogenic HLA kidney donors for UTMC patients, thus significantly improving their chances for long-term allograft survival.

Disparities in lung transplantation in children

Lung transplantation is a recognized therapy for end-stage respiratory failure in children and young people. It is only available in selected countries and is limited by access to suitable organs. Data on disparities in access and outcomes for children undergoing lung transplantation are limited. It is clear from data from studies in adults, and from studies in other solid organ transplants in children, that systemic inequities exist in this field. While data relating specifically to pediatric lung transplantation are relatively sparse, professionals should be aware of the risk that healthcare systems may result in disparities in access and outcomes following lung transplantation in children.

Impact of lung allocation policy change on Hispanic lung transplant outcomes: Addressing disparities and improving access

Objective

Racial disparities in organ allocation may result in differential survival for marginalized groups. This study aims to examine the impact of the November 2017 lung allocation policy change (LAPC) on trends and outcomes of Hispanic lung transplant (LT) recipients.

Methods

The United Network for Organ Sharing database was used to identify adult (older than age 18 years) LT recipients between January 2010 and March 2023. Recipients were categorized into 3 self-identified racial groups (Hispanic, non-Hispanic White, and non-Hispanic other). The Mann-Kendall trend test was used to assess the trend in rates of Hispanic LT over 5 years pre- and 5 years post-LAPC. The primary outcome was 1-year mortality.

Results

A total of 28,495 recipients from 80 centers were included, with 15,343 (53.8%) prepolicy change and 13,152 (46.2%) postpolicy change. The racial distribution of LT recipients was pre-LAPC: Hispanic: 1013 (6.6%), White: 12,601 (82.1%), Other: 1729 (11.3%) and post-LAPC: Hispanic: 1522 (11.6%), White: 9873 (75.0%), Other: 1757 (13.4%) (P < .001). Between 2013 and 2017, the proportion of Hispanic LT recipients increased from 6.0% to 7.6% (P = .221). Post-LAPC, the proportion increased from 8.5% in 2018 to 14.4% in 2022 (P < .027). Unadjusted 1-year survival rates were pre-LAPC: Hispanic: 88.8%, White: 87.6%, Other: 86.8% (log-rank P = .260) and post-LAPC: Hispanic: 90.6%, White: 88.2%, Other: 86.1% (log-rank P < .001).

Conclusions

The LAPC has led to increased access to LT and improved 1-year survival rates among Hispanic patients. However, efforts should continue to address disparities among other racial groups and ensure equitable outcomes for all recipients of LT.

Outcomes of Lung Transplant Candidates Aged ≥70 Years During the Lung Allocation Score Era

BACKGROUND

With the increasing age of lung transplant candidates, we studied waitlist and posttransplantation outcomes of candidates ≥70 years during the Lung Allocation Score era.

METHODS

Adult lung transplant candidates from 2005 to 2020 in the United Network for Organ Sharing database were included and stratified on the basis of age at listing into 18 to 59 years old, 60 to 69 years old, and ≥70 years old. Baseline characteristics, waitlist outcomes, and posttransplantation outcomes were assessed.

RESULTS

A total of 37,623 candidates were included (52.3% aged 18-59 years, 40.6% aged 60-69 years, 7.1% aged ≥70 years). Candidates ≥70 years were more likely than younger candidates to receive a transplant (81.9% vs 72.7% [aged 60-69 years] vs 61.6% [aged 18-59 years]) and less likely to die or to deteriorate on the waitlist within 1 year (9.1% vs 10.1% [aged 60-69 years] vs 12.2% [aged 18-59 years]; P < .001). Donors for older recipients were more likely to be extended criteria (75.7% vs 70.1% [aged 60-69 years] vs 65.7% [aged 18-59 years]; P < .001). Recipients ≥70 years were found to have lower rates of acute rejection (6.7% vs 7.4% [aged 60-69 years] vs 9.2% [aged 18-59 years]; P < .001) and prolonged intubation (21.7% vs 27.4% [aged 60-69 years] vs 34.5% [aged 18-59 years]; P < .001). Recipients aged ≥70 years had increased 1-year (adjusted hazard ratio [aHR], 1.19 [95% CI, 1.06-1.33]; P < .001), 3-year (aHR, 1.28 [95% CI, 1.18-1.39]; P < .001), and 5-year mortality (aHR, 1.29 [95% CI, 1.21-1.38]; P < .001) compared with recipients aged 60 to 69 years.

CONCLUSIONS

Candidates ≥70 years had favorable waitlist and perioperative outcomes despite increased use of extended criteria donors. Careful selection of candidates and postoperative surveillance may improve posttransplantation survival in this population.

Early experience of a new national lung allocation scheme in the UK based on clinical urgency

INTRODUCTION

A new UK Lung Allocation Scheme (UKLAS) was introduced in 2017, replacing the previous geographic allocation system. Patients are prioritised according to predefined clinical criteria into a three-tier system: the super-urgent lung allocation scheme (SULAS), the urgent lung allocation scheme (ULAS) and the non-urgent lung allocation scheme (NULAS). This study assessed the early impact of this scheme on waiting-list and post-transplant outcomes.

METHODS

A cohort study of adult lung transplant registrations between March 2015 and November 2016 (era-1) and between May 2017 and January 2019 (era-2). Outcomes from registration were compared between eras and stratified by urgency tier and diagnostic group.

RESULTS

During era-1, 461 patients were registered. In era-2, 471 patients were registered (19 (4.0%) SULAS, 82 (17.4%) ULAS and 370 (78.6%) NULAS). SULAS patients were younger (median age 35 vs 50 and 55 for urgent and non-urgent, respectively, p=0.0015) and predominantly suffered from cystic fibrosis (53%) or pulmonary fibrosis (37%). Between eras 1 and 2, the odds of transplantation within 6 months of registration were increased (OR=1.41, 95% CI 1.07 to 1.85, p=0.0142) despite only a 5% increase in transplant activity. Median time-to-transplantation during era-1 was 427 days compared with waiting times in era-2 of 8 days for SULAS, 15 days for ULAS and 585 days for NULAS patients. Waiting-list mortality (15% era-1 vs 13% era-2; p=0.5441) and post-transplant survival at 1 year (81.3% era-1 vs 83.3% era-2; p=0.6065) were similar between eras.

CONCLUSION

The UKLAS scheme prioritises the critically ill and improves transplantation odds. The true impact on waiting-list mortality and post-transplant survival requires further follow-up.

Tools and criteria to select patients with advanced Parkinson's disease for device-aided therapies: a narrative review

This article provides an overview of the various screening and selection tools which have been developed over the past 25 years to identify patients with Parkinson's disease (PD) possibly eligible for device-aided therapies (DATs). For the available screening tools, we describe the target therapies (subtypes of DAT), development methods, validation data, and their use in clinical practice. In addition, the historical background and potential utility of these screening tools are discussed. The challenges in developing and validating these tools are also addressed, taking into account the differences in population, the local health care organization, and resource availability.

Race-Specific Interpretation of Spirometry: Impact on the Lung Allocation Score

Rationale: Interpretation of spirometry using race-specific reference equations may contribute to health disparities via underestimation of the degree of lung function impairment in Black patients. The use of race-specific equations may differentially affect patients with severe respiratory disease via the use of percentage predicted forced vital capacity (FVCpp) when included in the lung allocation score (LAS), the primary determinant of priority for lung transplantation. Objectives: To determine the impact of a race-specific versus a race-neutral approach to spirometry interpretation on the LAS among adults listed for lung transplantation in the United States. Methods: We developed a cohort from the United Network for Organ Sharing database including all White and Black adults listed for lung transplantation between January 7, 2009, and February 18, 2015. The LAS at listing was calculated for each patient under race-specific and race-neutral approaches, using the FVCpp generated from the Global Lung Function Initiative equation corresponding to each patient's race (race-specific) or from the Global Lung Function Initiative "other" (race-neutral) equation. Differences in LAS between approaches were compared by race, with positive values indicating a higher LAS under the race-neutral approach. Results: In this cohort of 8,982 patients, 90.3% were White and 9.7% were Black. The mean FVCpp was 4.4% higher versus 3.8% lower among White versus Black patients (P < 0.001) under a race-neutral compared with a race-specific approach. Compared with White patients, Black patients had a higher mean LAS under both a race-specific (41.9 vs. 43.9; P < 0.001) and a race-neutral (41.3 vs. 44.3; P < 0.001) approach. However, the mean difference in LAS under a race-neutral approach was -0.6 versus +0.6 for White versus Black patients (P < 0.001). Differences in LAS under a race-neutral approach were most pronounced for those in group B (pulmonary vascular disease) (-0.71 vs. +0.70; P < 0.001) and group D (restrictive lung disease) (-0.78 vs. +0.68; P < 0.001). Conclusions: A race-specific approach to spirometry interpretation has potential to adversely affect the care of Black patients with advanced respiratory disease. Compared with a race-neutral approach, a race-specific approach resulted in lower LASs for Black patients and higher LASs for White patients, which may have contributed to racially biased allocation of lung transplantation. The future use of race-specific equations must be carefully considered.

National Trends, Risk Factors, and Outcomes of Acute In-Hospital Stroke Following Lung Transplantation in the United States: Analysis of the United Network for Organ Sharing Registry

BACKGROUND

Lung transplantation (LTx) is the definitive treatment for end-stage lung failure. However, there have been no large, long-term studies on the impact of acute in-hospital stroke in this population.

RESEARCH QUESTION

What are the trends, risk factors, and outcomes of acute stroke in patients undergoing LTx in the United States?

STUDY DESIGN AND METHODS

We identified adult first-time isolated LTx recipients from the United Network for Organ Sharing database, which comprehensively captures every transplant in the United States, between May 2005 and December 2020. Stroke was defined as occurring at any time after LTx but prior to discharge. Multivariable logistic regression with stepwise feature elimination was used to identify risk factors for stroke. Freedom from death in patients with a stroke vs those without a stroke was evaluated with Kaplan-Meier analysis. Cox proportional hazards analysis was used to identify predictors of death at 24 months.

RESULTS

Of 28,564 patients (median age, 60 years; 60% male), 653 (2.3%) experienced an acute in-hospital stroke after LTx. Median follow-up was 1.2 (stroke) and 3.0 (non-stroke) years. Annual incidence of stroke increased (1.5% in 2005 to 2.4% in 2020; P for trend = .007), as did lung allocation score and utilization of post-LTx extracorporeal membrane oxygenation (P = .01 and P < .001, respectively). Compared with those without stroke, patients with stroke had lower survival at 1 month (84% vs 98%), 12 months (61% vs 88%), and 24 months (52% vs 80%) (log-rank test, P < .001 for all). In Cox analysis, acute stroke conferred a high hazard of mortality (hazard ratio, 3.01; 95% CI, 2.67-3.41). Post-LTx extracorporeal membrane oxygenation was the strongest risk factor for stroke (adjusted OR, 2.98; 95% CI, 2.19-4.06).

INTERPRETATION

Acute in-hospital stroke post-LTx has been increasing over time and is associated with markedly worse short- and long-term survival. As increasingly sicker patients undergo LTx as well as experience stroke, further research on stroke characteristics, prevention, and management strategies is warranted.

Ultrasound Scanning in Lung Procurement. Protocol for Decision-Making With the Purpose of Increasing Transplant Eligible Lungs

BACKGROUND

The main obstacle to obtaining lungs for transplantation is the shortage of donors. Once potential donors have been offered to transplant programs, the acceptance rate is highly variable, ranging from 5% to 20%. Minimizing donor leakage by converting potential lung donors into real donors is one of the key elements to improve results, and it is essential to have tools that facilitate decision-making in this scenario. The selection and rejection of transplantation-eligible lungs are usually made with chest x-rays; however, lung ultrasound scanning has shown better sensitivity and specificity for diagnosing pulmonary pathologies. Lung ultrasound scanning allows us to identify the reversible causes of low PaO2/fraction of inspired oxygen (FIO2) ratio, thus enabling the establishment of specific interventions, which, if proved successful, could turn lungs into transplant-eligible lungs. The available literature on its use in managing brain death donors and lung procurement is extremely scarce.

METHODS

A simple protocol aimed at identifying and treating the main reversible causes of low PaO2/FIO2 ratio to aid in decision-making is presented in this paper.

CONCLUSION

Lung ultrasound is a powerful, useful, and cheap technique available at the donor's bedside. It is conspicuously underused, despite being potentially helpful in decision-making by minimizing the discarding of donors, thus probably increasing the number of lungs sui for transplantation.

Addressing sex-based disparities in liver transplantation

PURPOSE OF REVIEW

Disparities in access to liver transplantation by sex have been well described, disadvantaging women. Understanding the multifactorial causes of these disparities as well as the variety of proposed solutions is critical to improving access to this life-saving intervention for women. This review aims to summarize the current body of evidence on observed sex disparities in liver transplantation and highlight actionable, evidence-based mechanisms by which these disparities can be addressed.

RECENT FINDINGS

Strategies for addressing sex disparities in liver transplantation include increasing organ utilization, changing allocation policy, and leveraging public policies to reduce the incidence of end-stage liver disease. Several other promising interventions are currently being explored.

SUMMARY

In the United States, women face additional barriers to liver transplantation on the basis of sex. Immediate action is necessary to systematically address these inequities.

Modern outcomes of heart-lung transplantation: assessing the impact of the updated US allocation system

OBJECTIVES

In 2018, the United Network for Organ Sharing modified their heart allocation policy to reduce waitlist mortality and prioritize patients with the greatest acuity. Considering declining rates of combined heart-lung transplantation, this study sought to investigate the impact of the new allocation system on waitlist and post-transplant outcomes of patients listed for combined heart-lung transplantation.

METHODS

Adult patients listed for combined heart-lung transplant between 2012 and 2021 were included. Patients were stratified according to listing era. Competing risk regression was used to assess waitlist outcomes. Cox proportional hazards regression was used to establish risk factors for post-transplant mortality.

RESULTS

A total of 511 patients were included, of whom 295 (57.8%) were listed in era 1 and 216 (42.2%) in era 2. Era 2 was associated with increased likelihood of transplant (adjusted standard hazard ratio (aSHR): 1.60 [1.23-2.07]; P < 0.01) and decreased waitlist mortality (aSHR: 0.43 [0.25-0.73]; P < 0.01). Despite longer ischaemic times and increased use of preoperative veno-arterial extracorporeal membrane oxygenation (ECMO) in era 2, early post-transplant survival was equivalent. Predicted heart mass ratio <0.8 (Hazard ratio (HR); 3.24; P = 0.01), ventilator support (HR: 3.83; P < 0.01) and greater ischaemic times (HR: 1.80; P < 0.01) independently predicted the mortality. Procedures at high centre volumes (HR: 0.36; P = 0.04) were associated with decreased mortality. Use of ECMO was not predictive of mortality in the modern era.

CONCLUSIONS

The allocation policy change has led to improvements in waitlist outcomes in patients listed for heart-lung transplantation. Despite increased ischaemic times and use of ECMO, early post-transplant survival was equivalent.

Clinical impact of a modified lung allocation score that mitigates selection bias

BACKGROUND

The Lung Allocation Score (LAS) is used in the U.S. to prioritize lung transplant candidates. Selection bias, induced by dependent censoring of waitlisted candidates and prediction of posttransplant survival among surviving, transplanted patients only, is only partially addressed by the LAS. Recently, a modified LAS (mLAS) was designed to mitigate such bias. Here, we estimate the clinical impact of replacing the LAS with the mLAS.

METHODS

We considered lung transplant candidates waitlisted during 2016 and 2017. LAS and mLAS scores were computed for each registrant at each observed organ offer date; individuals were ranked accordingly. Patient characteristics associated with better priority under the mLAS were investigated via logistic regression and generalized linear mixed models. We also determined whether differences in rank were explained more by changes in predicted pre- or posttransplant survival. Simulations examined how 1-year waitlist, posttransplant, and overall survival might change under the mLAS.

RESULTS

Diagnosis group, 6-minute walk distance, continuous mechanical ventilation, functional status, and age demonstrated the highest impact on differential allocation. Differences in rank were explained more by changes in predicted pretransplant survival than changes in predicted posttransplant survival, suggesting that selection bias has more impact on estimates of waitlist urgency. Simulations suggest that for every 1000 waitlisted individuals, 12.8 (interquartile range: 5.2-24.3) fewer waitlist deaths per year would occur under the mLAS, without compromising posttransplant and overall survival.

CONCLUSIONS

Implementing a mLAS that mitigates selection bias into clinical practice can lead to important differences in allocation and possibly modest improvement in waitlist survival.

Outcomes of Patients on the Lung Transplantation Waitlist in Korea: A Korean Network for Organ Sharing Data Analysis

BACKGROUND

The demand for lung transplants continues to increase in Korea, and donor shortages and waitlist mortality are critical issues. This study aimed to evaluate the factors that affect waitlist outcomes from the time of registration for lung transplantation in Korea.

METHODS

Data were obtained from the Korean Network for Organ Sharing for lung-only registrations between September 7, 2009, and December 31, 2020. Post-registration outcomes were evaluated according to the lung disease category, blood group, and age.

RESULTS

Among the 1,671 registered patients, 49.1% had idiopathic pulmonary fibrosis (group C), 37.0% had acute respiratory distress syndrome and other interstitial lung diseases (group D), 7.2% had chronic obstructive pulmonary disease (group A), and 6.6% had primary pulmonary hypertension (group B). Approximately half of the patients (46.1%) were transplanted within 1 year of registration, while 31.8% died without receiving a lung transplant within 1 year of registration. Data from 1,611 patients were used to analyze 1-year post-registration outcomes, which were classified as transplanted (46.1%, n = 743), still awaiting (21.1%, n = 340), removed (0.9%, n = 15), and death on waitlist (31.8%, n = 513). No significant difference was found in the transplantation rate according to the year of registration. However, significant differences occurred between the waitlist mortality rates (P = 0.008) and the still awaiting rates (P = 0.009). The chance of transplantation after listing varies depending on the disease category, blood type, age, and urgency status. Waitlist mortality within 1 year was significantly associated with non-group A disease (hazard ratio [HR], 2.76, P < 0.001), age ≥ 65 years (HR, 1.48, P < 0.001), and status 0 at registration (HR, 2.10, P < 0.001).

CONCLUSION

Waitlist mortality is still higher in Korea than in other countries. Future revisions to the lung allocation system should take into consideration the high waitlist mortality and donor shortages.