Liver transplantationCandidateOverview of the MELD Score and the UNOS Adult Liver Allocation System
Section snippets
History of the Model for End-Stage Liver Disease
Over time, increasing evidence suggested that a prioritization system should allocate organs based on the need for a transplant, rather than on the waiting time. In 1999, a Liver Disease Severity Score (LDSS) Committee was formed within the Organ Procurement and Transplantation Network (OPTN), an institution administered by the United Network for Organ Sharing (UNOS). This committee was assigned the task to define a model that would accurately predict mortality on the waiting list. The Model
What is Meld?
The MELD score was first reported in 20002 to be a predictor of mortality risk among patients undergoing TIPS. It is an equation using 3 clinical laboratory measurements that were observed to have statistical impact on patient mortality risk (Table 1). The MELD score is currently considered to be the most accurate predictor of 90-day mortality risk for patients on the liver transplant waiting list. Before being validated and introduced in practice, the score was found to accurately predict
UNOS Territory
UNOS is a private, nonprofit organization that was contracted by the US Government to regulate and manage the organ allocation system in the United States. The territory of the United States is divided into 11 UNOS regions. Within each region, there are several Organ Procurement Agencies (OPO). Each OPO serves several transplant centers within their territory. The OPO centralizes the patients from the waiting lists of all centers within its territory and grants them priority by MELD score, so
How Does the Allocation System Work?
Patients are prioritized on the waiting list within each blood type group by descending MELD score. This implies that the organs are basically allocated to the waitlisted patients with the highest mortality risk at the given time. Within each MELD score, livers are first allocated to blood type-identical patients. To prevent inequitable distribution of organs, blood type O livers may only be attributed to blood type O recipients. The system allows patients with special situations (like very
Too Healthy Versus Too Sick
One of the problems that has been raised is the balance between allocating the organs to the sickest patients (with the drawback of poorer posttransplantation outcome) versus allocating them to patients who would benefit most from transplantation by having the best survival rates. The interest of a liver transplant candidate is best served when the expected survival is higher than that without transplantation. It has been shown that among patients with MELD scores under 15, the mortality risk
Meld Exceptions
It is recognized that there are categories of patients whose MELD scores do not reflect the true urgency of their need for transplantation. Several categories of patients qualify under current regulations for various degrees of upgrading of their MELD scores to values that would allow them to undergo transplantation within a predictable time frame. Examples of exceptions include patients with hepatocellular carcinoma (HCC); biliary strictures; recurrent biliary sepsis; refractory upper
Transplantation of Patients with HCC
Prioritization of patients with HCC is one of the most debated topics. Under the previous organ allocation system, Yao et al10 found a 25% yearly dropout rate from the waiting list due to progressive disease. Still, putting these patients at advantage may diminish the chances of otherwise sicker candidates to receive an organ in time. Currently, T2 tumors (namely, 1 nodule 2.0 to 5.0 cm: 2 or 3 nodules, all <3.0 cm as defined by the American Liver Tumor Study Group Modified
Meld and Retransplantation
Retransplanted patients tend to have a poorer outcome than patients undergoing a first liver transplantation. Data reported by Edwards and Harper in a study based on OPTN data13 showed that the MELD scores of retransplanted patients were higher than those of first-transplant patients. Also, in patients with MELD scores higher than 20, the relative risk of death on the waiting list was higher for relisted patients at similar MELD scores. Similar data were reported by other authors.14 These
Improving the Predictive Accuracy of the MELD Score
Several factors have been studied as potential elements to improve the estimation of pretransplantation mortality. There are data to suggest that the change in MELD or PELD scores over short periods may correlate with higher mortality risk on the waiting list.15, 16 Ascites, encephalopathy, and variceal bleeding do not add significant improvement to the statistical performance of MELD. Serum sodium seems to be a reliable surrogate for ascites. In one single-center study, hyponatremia correlated
Transplant Statistics in the MELD Era
After the implementation of MELD as the basis of organ allocation, a large amount of statistical work has been done to follow the results of this change on organ distribution.
Future Trends
Even if the new organ allocation policy is considered to be an improvement in comparison to the waiting time-based prioritization, it is still far from perfect. There are still many areas of concern and many discrepancies. Inter- and intraregional differences in number and size of transplant centers, as well as in the efficiency of OPOs, make a difference in the patients’ chances of receiving a transplant and in the average transplantation MELD scores.6, 18 Thus, patients with equal MELD scores
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Cited by (58)
Liver Severity Score-Based Modeling to Predict Six-Week Mortality Risk Among Hospitalized Cirrhosis Patients With Upper Gastrointestinal Bleeding
2024, Journal of Clinical and Experimental HepatologyValidation of the Model for End-Stage Liver Disease 3.0 in Korean Patients on the Liver Transplant Waiting List
2023, Clinical Gastroenterology and HepatologySystemic Immune-Inflammatory Marker of High Meld Patients Is Associated With Early Mortality After Liver Transplantation
2021, Transplantation ProceedingsMELD and MELD XI Scores as Predictors of Mortality After Pericardiectomy for Constrictive Pericarditis
2021, Mayo Clinic ProceedingsCitation Excerpt :Per the United Network for Organ Sharing (UNOS) modification, variable lower limits were set at 1.0 and the creatinine upper limit set at 4.0 mg/dL. Subjects receiving preoperative dialysis were assigned creatinine levels of 4.0 mg/dL.27 We conducted the primary analyses using a 90-day end point for operative mortality, as defined by death from any cause occurring within 90 days or during the hospitalization for the pericardiectomy.
Systemic therapy of liver cancer
2021, Advances in Cancer ResearchCitation Excerpt :The Barcelona Clinic Liver Cancer (BCLC) stage is the staging system that involves these factors and is widely used for selecting treatment plans (Llovet, Bru, & Bruix, 1999). Transplant decisions frequently use criteria from the United Network for Organ Sharing (UNOS) and Model for End-Stage Liver Disease (MELD) scores (Kaseb, Abaza, & Roses, 2013; Martin, Bartels, Hauss, & Fangmann, 2007). Hepatocellular carcinoma (HCC) is the most common liver cancer and is the fourth leading cause of cancer-related deaths worldwide (Siegel, Miller, & Jemal, 2020).