MELD–Na as a prognostic score for cirrhotic patients: Hyponatremia and ascites are back in the game

For several decades now, the severity of cirrhosis has been scored using the Child–Pugh system []. Use of this score became widespread because of its simplicity and its good correlation with long-term outcome in cirrhotic patients. The Mayo End-stage Liver Disease score (MELD) was initially employed to determine the prognosis of cirrhotic patients treated by means of a transjugular portacaval shunt (TIPS) []. This more recent score comprises three variables: bilirubin levels, INR and creatinine levels. However, the latter variable is not included in the Child–Pugh scoring system. MELD is a quantitative tool with scores ranging from 5 to 40, a maximum score being indicative of the most severe stage. The popularity of this more recent score has arisen firstly, from its linear correlation with a quantitative value and a risk of death within 3 months [], and secondly because of the decision by the US health authorities in 2002 to allocate liver grafts as a function of cirrhosis severity. This new system of allocating grafts to more severe patients evaluated using the MELD score resulted in a dramatic decrease in waiting list mortality without significantly impairing post-transplant outcome []. It has also resulted in a reduction in the number of less severely affected patients being placed on the transplant waiting list. In addition, it has been suggested that patients in the US with a MELD score lower than 15 have a greater risk of death at one year as a result of the transplant procedure itself rather than not undergoing transplantation, suggesting that these patients should not be put on the waiting list []. The problem with this affirmation is that it only takes survival at one year and no further into account. Thus most countries have now decided to apply a similar system for graft allocation; this is based on the MELD score or on a composite score that includes the MELD. Unfortunately, this graft allocation system has several major drawbacks: it only applies to patients with cirrhosis; those with hepatocellular carcinoma on compensated cirrhosis, sclerosing cholangitis, metabolic disease or various other rare conditions that are not classified accurately by the MELD score and their access to liver transplantation is problematic []. For this reason, an artificial MELD score was developed for HCC patients, taking into account the risk of drop out from the waiting list by these patients []. For other patients, such as those with metabolic disease, refractory ascites or recurrent encephalopathy despite a low MELD score, the only means of ensuring their access to transplantation was to request their prioritization by an expert committee. Returning to cirrhotic patients, several authors raised the point that the Child–Pugh score also takes account of the presence of ascites, low albumin levels and encephalopathy, and that these three features are absent from the MELD score. Because the volume of ascites is a subjective sign, it was suggested that Na values should be added to the MELD score in order to allow for the presence of refractory ascites or hepatorenal syndrome (HRS) [, , ]. Indeed, hyponatremia is associated with a higher risk of complications with ascites and the onset of HRS []. In view of these arguments, Kim et al. analyzed the prognostic value of hyponatremia at levels between 125 and 140 Meq/l. They built a model that considered the prognostic value of both hyponatremia and MELD, and developed a new scoring system called MELD–Na. Calculation of this score was based on data concerning patients placed on the US waiting list in 2005, as follows: MELD–Na = MELD − Na − [0.025 × MELD × (140 − Na)]  + 140. They then applied this new score to the cohort of cirrhotic patients placed on the US liver transplant waiting list in 2006. They showed that MELD and hyponatremia were correlated with the mortality risk, and also demonstrated that the MELD–Na score was more predictive of the risk of death in more severe patients, and particularly those with a MELD score of between 20 and 39 []. The presence of hyponatremia thus adds points to the current MELD score, so that a patient with hyponatremia will have a higher MELD–Na score than the same patient with normal serum sodium levels. As a result, refractory ascites has recovered indirectly its importance to scoring, as suggested by the Child–Pugh score.

This new score needs to be validated in additional independent cohorts, and it will be interesting to determine whether it will benefit the more severely affected patients only, or the entire cohort of cirrhotic patients. We should acknowledge the constant efforts of our US colleagues to improve prognostic scoring systems for cirrhotic patients, so that the more severe amongst them will benefit from better access to transplantation. However, it is also important to apply this new score to a variety of cirrhotic patient cohorts and to different etiologies of the disease, and to determine the prognostic value of the MELD–Na score not only in the short-term but also in the medium and longer terms. We need to decide whether this new score should be implemented for allocation by organ-sharing organizations, and clarify how it might impact waiting list mortality and post-transplant outcome.