The MELD score in patients awaiting liver transplant: strengths and weaknesses.

Adoption of the Model for End-stage Liver Disease (MELD) to select and prioritize patients for liver transplantation represented a turning point in organ allocation. Prioritization of transplant recipients switched from time accrued on the waiting list to the principle of "sickest first". The MELD score incorporates three simple laboratory parameters (serum creatinine and bilirubin, and INR for prothrombin time) and stratifies patients according to their disease severity in an objective and continuous ranking scale. Concordance statistics have demonstrated its high accuracy in stratifying patients according to their risk of dying in the short-term (three months). Further validations of MELD as a predictor of survival at various temporal end-points have been obtained in independent patient cohorts with a broad spectrum of chronic liver disease. The MELD-based liver graft allocation policy has led to a reduction in waitlist new registrations and mortality, shorter waiting times, and an increase in transplants, without altering overall graft and patient survival rates after transplantation. MELD limitations are related either to the inter-laboratory variability of the parameters included in the score, or to the inability of the formula to predict mortality accurately in specific settings. For some conditions, such as hepatocellular carcinoma, widely accepted MELD corrections have been devised. For others, such as persistent ascites and hyponatremia, attempts to improve MELD's predicting power are currently underway, but await definite validation.