MELD and PELD: Application of survival models to liver allocation

Compared to the CTP score (Table 9), the MELD and PELD models provide the means to more accurately measure liver disease severity and to better predict which patients are at risk of dying on the waiting list. The relation between the MELD score and the risk of 3-month mortality is shown in Fig. 7. Most importantly, by de-emphasizing waiting time these two models will allow organ allocation based on medical urgency, as mandated in the DHHS final rule. However, while the MELD score is an extremely powerful predictor of the probability of death in patients with chronic liver disease, it does not address one of the guidelines in the final rule, that an organ allocation system should promote the most efficient use of scarce donor resources and should avoid futile transplants. Thus, a future challenge will be to modify the MELD model in order to predict the probability of death with and without a liver transplant and thus to allow further optimization of the timing of this life-saving procedure. Finally, ongoing studies are needed to further define when the severity of liver disease of a patient has deteriorated to the point that the transplant procedure itself becomes futile. Hopefully, ongoing data collection, as mandated by the Final Rule of HHS, can help us address some of these extremely complex and challenging issues.