The Model for End-Stage Liver Disease (MELD) score was originally developed in 2000 to predict 3-month mortality in patients undergoing TIPS (transjugular intrahepatic portosystemic shunting) procedures, then validated as a superior predictor of waitlist mortality compared to the Child-Pugh score. UNOS adopted MELD for organ allocation in 2002, replacing the Child-Pugh/MELD hybrid system. The score uses three objective laboratory variables: serum bilirubin, international normalised ratio (INR), and serum creatinine — all reflecting different aspects of hepatic and renal function. MELD-Na (incorporating sodium) was adopted by UNOS in 2016 as it better predicts 90-day waitlist mortality.