In 2005, the United States’ federal government developed a new allocation system for lung transplantation.
The system used predictive models to estimate the patient’s risk for death without transplantation and the net benefit, or the extent to which survival is increased with transplantation.
A lung allocation score (LAS) is calculated based on these survival predictions and then normalized to a number between 0 and 100 for easier interpretation. The system is intended to identify the sickest patients who would benefit the most and eliminate those whose probable outcomes are so poor that resources should be conserved.
These scores were assigned to patients 12 years or older because there were insufficient data to support the validity of the predictive models in younger patients. This deficiency prompted the Organ Procurement and Transplantation Network (OPTN) to establish a separate system of priority ranking for children under 12.
The average waiting time for lung transplantation after implementing this new system dropped from 2 to 3 years to less than 200 days. Importantly, the mortality rate of patients on the waiting list has dropped significantly because as the patient gets sicker, their LAS score increases, placing the patient higher on the list.