The Lung Allocation Score and its Impact on Lung Transplantation for Chronic Obstructive Pulmonary Disease

Abstract

Charged with reducing the wait-list mortality while prioritizing candidates by medical urgency, the Organ Procurement and Transplantation Network in May of 2005 enacted an allocation system for the utilization of donor lungs within the United States. As a result, lung transplant candidates are now assigned a lung allocation score (LAS) that is used to prioritize and match these candidates with available donor lungs.

Analysis of the early data that has been collected since the LAS took affect has indeed revealed a reduction in wait-list mortality as well as a clear change in the distribution of available organs among those with differing types of advanced lung disease. Scores of those candidates on the wait-list have generally increased over time with most of the increase due to certain patient groups such as cystic fibrosis (CF) and idiopathic pulmonary fibrosis (IPF), but without a concomitant rise in wait-list mortality. As a result of increasing scores in these groups, those with IPF are receiving an increasing proportion of available donor lungs while those with other lung diseases such as COPD are receiving fewer.

Following transplantation, those candidates who had higher scores may be at risk for more postoperative complications such as primary graft dysfunction and extended ICU stays. This finding has been especially notable in the group with IPF. While no LAS has been demonstrated to be prohibitively high, several investigators have reported a significant increase in 1-year posttransplant mortality for those with exceedingly high candidate scores. Some have even suggested that scores as low as 46 may be associated with increased postoperative mortality.

While lung transplantation for COPD has not been demonstrated to extend survival when compared to the course of the native disease, those who have received a transplant have generally experienced superior early survival when compared to other disease groups who receive lung transplants. This is especially notable for those with COPD who receive bilateral lung allografts where 1-year posttransplant survival rates exceed 83%. In addition to improved early survival, posttransplant interventions such as pulmonary rehabilitation may significantly enhance recipient quality of life by addressing both functional and psychosocial parameters. The results of these observations are likely to continue to stimulate debate as to whether the new allocation system affords the best use of available donor organs.

Keywords

lung allocation score, COPD, lung transplantation