Supplementary Material for: A Simplified Score for Extended Donor Criteria in Times of Organ Shortage

Background: Lung transplantation (LT) remains the gold standard treatment for patients with end-stage lung disease, but persistent organ shortage challenges equitable organ allocation. While post-transplant survival has been well characterized in the U.S., data from corresponding cohorts remain limited. This study analyzed three-year survival outcomes among German LT recipients and explored a simplified donor-recipient hazard score with a particular focus on rescue allocation. Methods: We retrospectively analyzed 999 patients who underwent LT in Germany between 2006 and 2016 using data from the German Transplant Registry. Univariate and multivariate analyses were performed to identify survival predictors. A simplified hazard score was developed using Cox regression and validated with C-index and Brier scores. Results: Rescue allocation was applied in 42.3% of cases and was independently associated with improved survival (HR 0.64, 95% CI 0.49–0.85, p=0.002). Additional factors associated for mortality included donor smoking (HR 1.37, p=0.03), lung allocation score (LAS) >55 (HR 1.85, p<0.001), total lung capacity ratio ≤0.86 (HR 1.45, p=0.03), and donor age >55 (HR 1.24, p=0.11). A simplified hazard score was derived from these variables, with absence of rescue allocation contributing one point. Three-year survival declined to 56% (95% CI 49–64%) when more than two risk factors were present. Conclusion. This study identifies key donor and recipient factors associated with three-year survival after lung transplantation in Germany. Rescue allocation was frequently applied and unexpectedly associated with improved survival outcomes in this cohort. The hazard score, showing moderate discrimination (C-index = 0.62), should be regarded as an exploratory clinical decision-support tool requiring external validation. These findings highlight the complexity of organ allocation under the current LAS system and underscore the need for ongoing evaluation of LAS policies in settings of organ shortage.