Disparities in the Lung Allocation Score Due to Geography Have Not Changed Since November 2017

Abstract

Differences in geographic donor lung availability affect waitlist outcomes. We hypothesized that the lung allocation score (LAS) at transplant and waitlist time would vary based on local donor lung availability and that broader geographic sharing since November 2017 would improve these disparities. Using UNOS data, we conducted a retrospective cohort study of 23,414 lung transplant recipients from January 1, 2006 - December 31, 2018. Local lung availability was defined as the ratio of donor lungs to waitlist candidates in the local donation service area. We calculated the local lung availability for candidates prior to November 25, 2017. We used mixed multivariable linear regression and Poisson regression, adjusting for time dependent LAS changes, to examine the relationship between local lung availability, LAS at transplant and waitlist time. We used Wilcoxon rank-sum to compare LAS at transplant before and after November 2017. Compared to recipients in the top quartile with greatest local lung availability, recipients in the lowest quartile were transplanted with a LAS 6.2 points higher (95% CI: 5.6-6.9, p <0.001) and waited significantly longer, 186 days (95% CI: 178-194) compared with 93 days (95%CI: 88-97), p <0.001. This difference varied by transplant type, with single lungs recipients transplanted with a LAS 2.0 points higher in the lowest quartile (95%CI: 0.9-3.0, p < 0.001) compared with the top and double lung recipients transplanted with a LAS 8.8 points higher (95% CI: 8.0-9.6, p<0.001) in the lowest quartile compared with the top. At centers in the lowest quartile of local lung availability, the LAS at transplant did not meaningfully change after November 2017 (44.1 ± 15.2, compared to 45.7± 16.3, p=0.042), however the waitlist time did decrease from 206 days (95%CI: 192-222) to 155 days, (95% CI: 133-176), p <0.001. The LAS at transplant and waitlist time for recipients did not change at high local lung availability centers (50.7 ± 19.6 compared to 51.3 ± 19.6, p=0.38, and 74 days (95%CI: 66-81) compared to 61 days (95%CI: 52-70), p=0.66). Prior to November 2017, low local lung availability was associated with longer waitlist times and higher LAS at transplant that were much more pronounced for double lung recipients. Since expanding allocation to 250 miles, meaningful differences in LAS at transplant have not yet been observed.