Assessing liver dysfunction in cirrhosis: role of the model for end-stage liver disease and its derived systems

The model for end-stage liver disease (MELD) has replaced the role of the Child-Turcotte-Pugh system as a more commonly used system in evaluating the severity of liver dysfunction in patients with chronic liver disease, owing to its superior ability to predict survival. The United Network of Organ Sharing (UNOS) in the USA has used the MELD system for prioritizing donor grafts in advanced cirrhotic patients awaiting liver transplantation since 2002. Serum sodium level is another important prognostic predictor in cirrhosis. Consequently, by incorporating serum sodium into the original MELD, the MELD-Na, MELDNa, the MELD-to-sodium ratio (MESO) index, and the ReFit MELDNa were proposed in an attempt to improve the predictive ability of the original MELD. Nevertheless, there are some limitations of the MELD-based systems that need to be refined. The MELD-based systems merely use laboratory data as parameters for the equation, therefore, any lack in unification and standardization of laboratory methods will result in inconsistent data that affect the prioritization of liver transplantation. Furthermore, the MELD system includes creatinine as a parameter, and serum creatinine level may represent different degrees of renal dysfunction in men and women. Therefore, these limitations may compromise the fair process of organ allocation for female cirrhotic patients. Currently, the application of the MELD system has been extended to tumor staging of hepatocellular carcinoma. Several studies have replaced the Child-Turcotte-Pugh system with the MELD as a parameter, indicating that the use of different criteria of liver dysfunction in cancer staging may enhance prognostic accuracy. Although the outcome data of the modified staging systems need to be confirmed, the concept of using the MELD as a reference system for evaluating the severity of liver dysfunction has globally become an important issue.