Since 2002, liver allocation for adults in the United States has been based on the Model for End-stage Liver Disease (MELD) score. The MELD formula, which is calculated on the basis of 3 objective variables (creatinine, bilirubin, and INR), predicts liver transplant survivability of patients waiting for liver transplantation, with higher MELD scores associated with higher mortality rates.
For patients with certain conditions (e.g., hepatocellular carcinoma), special scoring modifications are made.
The MELD score replaced the previous Status 2A, 2B and 3 categories. The most medically urgent category – Status 1, for patients with acute failure and a life expectancy of less than 7 days without a transplant, as well as for transplant recipients with primary non-function of their graft – is still used to indicate the highest priority and has not been affected by MELD.
Time on the waiting list is only used to break ties between two or more patients with the same MELD score and the same blood type. The maximum MELD score is 40. Within a given organ procurement area, patients with a higher MELD score always rank ahead of those with lower scores, even if some patients with lower scores have waited longer.
For children under 18, livers are allocated according to the Pediatric End-stage Liver Disease score (PELD). PELD is similar to MELD but also includes criteria related to pediatric growth issues (i.e., albumin level, growth failure, and age less than 12 months).
Each patient’s MELD or PELD score must be updated according to a schedule set by UNOS, ranging from weekly (for patients with higher MELD scores) to annually (for patients with MELD scores <10). MELD scores automatically revert to the previous lower score if the updated score is not registered with UNOS.
For further information and automated MELD calculations for liver transplant survivability go to www.unos.org/resources.