ABO blood group-related waiting list disparities in liver transplant candidates: effect of the MELD adoption

Background. Blood group O candidates remain on the waiting list for a liver transplant for a longer time than candidates of other blood groups. Herein, we analyzed potential factors affecting waiting times in the period that preceded the introduction of the model for end-stage liver disease (MELD) and in MELD era, remarking possible corrections introduced by the adoption of the MELD. Methods. Our analysis was entirely based on data obtained from the "Organ Procurement and Transplantation Network", referring to the periods before and after the adoption of the MELD. Results. In the MELD era, taking into consideration all candidates, the cumulative probability of remaining on the waiting list significantly diminished whereas that of undergoing transplantation significantly increased when compared with the pre-MELD era. However, group O candidates maintained the lowest cumulative probability of undergoing liver transplant, in all MELD classes, and the highest percentage of list removal for death/too sick. What caused the highest disadvantage for group O, in both eras, was the use of group O organs for ABO-compatible transplants, even in the absence of urgency. In candidates receiving ABO-compatible organs a significantly lower graft survival rate was observed compared with candidates receiving ABO-identical organs, even when the analysis was adjusted for the MELD score. Conclusions. The introduction of the MELD significantly reduced the waiting time for all candidates as also the shift of group O organs. Limiting ABO-compatible organs exclusively to urgent cases would have a positive effect not only in terms of individual justice, but also terms of in general utility, considering the effect of ABO-matching on graft survival.