Allograft discard risk index for lung transplantation

The demand for donor lungs continues to outpace the supply, yet nearly 75% of donor lungs intended for lung transplantation are discarded.

We reviewed all donation after brain death organ donors listed within the UNOS Deceased Donor Database between 2005 and 2020. Univariable and multivariable analyses were run on the training set (n = 69,355) with the primary outcome defined as lung discard, and the results were used to create a discard risk index (DSRI). Discard data were assessed at DSRI value deciles using the validation set (n = 34,670), and differences in 1-year mortality were assessed using stratum-specific likelihood ratio (SSLR) analysis.

Donor factors most associated with higher DSRI values included age > 65, PaO₂ < 300, hepatitis C virus, and cigarette use. Factors associated with lower DSRI values included donor age < 40 and PaO2 > 400. The DSRI was a reliable predictor of donor discard, with a C-statistic of 0.867 in the training set and 0.871 in the validation set. The DSRI was not a reliable predictor of 30-day, 1-year, 3-year, and 5-year survival following transplantation (C-statistic 0.519-0.530). SSLR analysis resulted in three 1-year mortality strata (SSLR 0.88 in the 1st DSRI value decile, 1.03 in the 2nd-5th, & 1.19 in the 6th-10th).

The factors leading to lung allograft discard are not the same as those leading to worse recipient outcomes. This suggests that with proper allocation, many of the grafts that are now commonly discarded could be used in the future donor pool with limited impact on mortality.