Risk Stratification of Lung Transplant Candidates: Implications for

In response to perceived inequities of the existing time-based system, and under mandate of the federal govern-ment, a new lung allocation system was introduced in the United States in 2005. This system allocates organs on the basis of medical urgency (risk for death without transplan-tation) and “net transplant benefit ” (the extent to which survival is increased with, as opposed to without, trans-plantation). It uses predictive models, incorporating more than a dozen variables, to generate predictions of 1-year survival with and without transplantation for a given pa-tient (1). A raw lung allocation score (LAS) is calculated on the basis of these survival predictions and normalized to a scale of 0 to 100 for ease of use. Because 1-year survival without transplantation is factored into net transplant ben-efit and medical urgency measures, it affects the LAS more than posttransplantation survival, which is used only in th