This article was updated Nov. 5, 2021.
A newly updated version of the Model for End-Stage Liver Disease (MELD) score was effective for predicting short-term mortality in patients with end-stage liver disease and addressed important determinants of wait list outcomes that haven’t been addressed in previous versions, according to findings from a recent study. The new model, termed MELD 3.0, includes new variables such as female sex, serum albumin, and updated creatinine cutoffs.
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“We believe that the new model represents an opportunity to lower wait list mortality in the United States and propose it to be considered to replace the current version of MELD in determining allocation priorities in liver transplantation,” wrote study authors W. Ray Kim, MD, of Stanford (Calif.) University and colleagues in Gastroenterology.
In patients with end-stage liver disease, the MELD score was shown to be a reliable predictor of short-term survival, according to the researchers. The original version of MELD consists of international normalized ratio of prothrombin time and serum concentrations of bilirubin and creatinine; MELDNa consists of the same with the addition of serum concentrations of total sodium. Since 2016, MELDNa has been utilized in the United States to allocate livers for transplant.
Despite the utility of the current MELD score, questions have been raised concerning the accuracy of the tool’s ability to predict mortality, including a study by Sumeet K. Asrani, MD, MSc, and colleagues. Changes in liver disease epidemiology, the introduction of newer therapies that alter prognosis, as well as increasing age and prevalence of comorbidities in transplant-eligible patients are several drivers for these concerns, according to Dr. Kim and colleagues. Also, there is an increasing concern regarding women and their potential disadvantages in the current system: At least one study has suggested that serum creatinine may overestimate renal function and consequently underestimate mortality risk in female patients, compared with men with the same creatinine level.
Dr. Kim and colleagues sought to further optimize the fit of the current MELD score by considering alternative interactions and including other variables relevant to predicting short-term mortality in patients awaiting liver transplant. The study included patients who are registered on the Organ Procurement and Transplantation Network Standard Transplant Analysis and Research files newly wait-listed from 2016 through 2018. The full cohort was divided 70:30 into a development set (n = 20,587) and a validation set (n = 8,823); there were no significant differences between the sets in respect to age, sex, race, or liver disease severity.
The investigators used univariable and multivariable regression models to predict 90-day survival following wait list registration. The 90-day Kaplan-Meier survival rate in the development set was 91.3%. Additionally, model fit was tested, and the investigators used the Liver Simulated Allocation Model to estimate the impact of replacing the current version of the MELD with MELD 3.0.
In the final MELD 3.0 model, the researchers included several additional variables such as female sex and serum albumin. Additionally, the final model was characterized by interactions between bilirubin and sodium as well as between albumin and creatinine. Also, an adjustment to the current version of MELD lowering the upper bound for creatinine from 4.0 mg/dL to 3.0 mg/dL.
The MELD 3.0 featured significantly better discrimination, compared with the MELDNa (C-statistic = 0.8693 vs. 0.8622, respectively; P < .01). In addition, the researchers wrote that the new MELD 3.0 score “correctly reclassified a net of 8.8% of decedents to a higher MELD tier, affording them a meaningfully higher chance of transplantation, particularly in women.” The MELD 3.0 score with albumin also led to fewer wait-list deaths, compared with the MELDNa, according to the Liver Simulated Allocation Model analysis (P = .02); the number for MELD 3.0 without albumin was not statistically significant.
According to the investigators, a cause of concern for the MELD 3.0 was the addition of albumin, as this variable may be vulnerable to manipulation. In addition, the researchers note that, while differences in wait list mortality and survival based on race/ethnicity were observed in the study, they were unable to describe the exact root causes of worse outcomes among patients belonging to minority groups. “Thus, inclusion in a risk prediction score without fully understanding the underlying reasons for the racial disparity may have unintended consequences,” the researchers wrote.
“Based on recent data consisting of liver transplant candidates in the United States, we identify additional variables that are meaningfully associated with short-term mortality, including female sex and serum albumin. We also found evidence to support lowering the serum creatinine ceiling to 3 mg/dL,” they wrote. “Based on these data, we created an updated version of the MELD score, which improves mortality prediction compared to the current MELDNa model, including the recognition of female sex as a risk factor for death.”
The researchers reported no conflicts of interest with the pharmaceutical industry. No funding was reported for the study.