Current status of thoracic organ transplantation and allocation in the United States

Abstract

The new Lung Allocation Score (LAS) system was created to address issues related to extended candidate waiting time, limited organ supply, waitlist mortality, and post-transplant survival. All candidates age 12 and older will be assigned an LAS that determines their priority for receiving lung offers. Waiting time will no longer play a factor in allocating organs to these candidates. Pediatric candidates under age 12 will continue to be allocated donor lungs based primarily on their accumulated waiting time. The LAS is the end product of an algorithm that assigns priority to lung candidates who are at higher risk of death if they do not receive a transplant (waitlist urgency) and who are likely to receive a greater benefit of longer lifetime with a transplant than without a transplant (transplant benefit). A variety of clinical factors, including disease diagnosis, were found to be predictive of waitlist urgency and post-transplant survival among transplant candidates, and are used in the calculation of each candidate's LAS. Pediatric and adolescent lung transplant candidates will have first priority for receiving offers from pediatric and adolescent lung donors. The lung allocation system will undergo frequent periodic reviews by OPTN/UNOS Committees to ensure that the performance goals of the system are being met and to address modifications to the system as they become necessary. The heart allocation system is an urgency status system under which adult and pediatric candidates are prioritized for organ offers by increasing levels of medical urgency. Median waiting time to transplant is shortest in the more medically urgent categories: Adult Status 1A=52 days, 1B=82 days, 2=468 days; Pediatric Status 1A=53 days, 1B=61 days, 2=149 days. Mortality among adult candidates after listing is strongly influenced by the medical urgency status at listing. Similarly mortality after transplantation for adult recipients also appears to be affected by the medical urgency status at transplant.