New MERD Risk Score Predicts Mortality for Kidney Transplant Waitlist Patients

A newly developed risk score using national Organ Procurement and Transplantation Network (OPTN) data demonstrated fair accuracy in predicting short-term mortality among > 147,000 adult kidney transplant waitlist candidates.1

The Mortality Estimation in Renal Disease (MERD) score aims to help guide the allocation of expanded criteria donor kidneys to candidates at the highest mortality risk, while acknowledging further prospective validation and model refinement are warranted.1

“In this study, we aim to develop an index score utilizing variables from the OPTN database to predict mortality among adult kidney transplant candidates within 3 years of being on the waitlist,” wrote Aisha Albu Mustaf, MBBS, University of Baghdad College of Medicine, and colleagues.1

Kidney transplant candidates face a risk of mortality while on the waitlist before receiving an allograft. Despite existing risk prediction tools, there is currently no widely adopted system that reliably identifies patients at the highest risk of waitlist mortality, particularly given the ongoing shortage of living donor organs.1,2

To address this, investigators conducted a retrospective analysis of adult kidney transplant candidates using data from the OPTN database between 2018 and 2023.1

Investigators evaluated 16 demographic and clinical variables using univariate logistic regression to identify factors associated with kidney transplant waitlist mortality. Variables demonstrating statistical significance were subsequently entered into a multivariable logistic regression model to develop the MERD score, a predictive tool designed to estimate short-term waitlist mortality risk. Model performance was assessed using receiver operating characteristic (ROC) curve analysis, with discrimination quantified by the C-statistic.1

Investigators randomly divided kidney transplant candidates into training and validation cohorts to evaluate internal validity. Mortality risk stratification was further examined by categorizing candidates into MERD score quartiles, with cumulative mortality compared across quartiles over time.1

The study included data from 147,307 adults ≥ 18 years of age who were waitlisted kidney transplant candidates. The age of the patient population ranged between 45 and 54 years (21.21%). Only 6.67% of candidates were ≥ 70 years, while 9.46% were young adults aged 18 to 34 years.1

Among the adult kidney transplant candidates included from the OPTN database, Mustaf and colleagues identified 10 variables as significant predictors of waitlist mortality and incorporated them into the Mortality Estimation in Renal Disease (MERD) score. These included age, ABO blood type, ethnicity, dialysis duration, presence of peripheral vascular disease, serum albumin level, functional status, prior kidney malignancy, primary etiology of kidney disease, and insurance type.1

The investigators reported age and etiology of kidney disease accounted for the largest proportion of the model’s predictive contribution. In multivariable analyses, Mustaf and colleagues found young adults 18 to 34 years, blood types A and AB, African American, Hispanic Latino, and Asian ethnicity relative to White ethnicity, preserved functional status, and higher serum albumin levels were associated with lower waitlist mortality.1

In contrast, age >55 years, White ethnicity, longer dialysis duration, reduced functional status, low albumin levels, diabetes, and the presence of peripheral vascular disease were associated with an increased risk of mortality.1

According to the investigators, the MERD score demonstrated fair discriminatory performance for predicting waitlist mortality, with an area under the curve (AUC) of 0.6657 in the training cohort and 0.6580 in the validation cohort. Model performance was consistent between cohorts, supporting internal validity.1

When candidates were stratified by MERD score quartiles, the investigators observed cumulative mortality increased progressively with higher scores. Candidates in the highest MERD quartile experienced the greatest proportion of mortality over follow-up, indicating the model’s ability to stratify short-term mortality risk among kidney transplant waitlist candidates.1

“The MERD score provides proof of concept for short-term mortality prediction for kidney transplant waitlist candidates. Further prospective validation and model refinement are warranted,” concluded investigators.1

References

1. Albu Mustaf A, Ramirez J, Montgomery A, Henry G, Rana A. Mortality Estimation in Renal Disease (MERD Score): A Model Predicting Waitlist Mortality in Kidney Transplant Candidates. Transplantation Proceedings. Published online January 8, 2026. doi:https://doi.org/10.1016/j.transproceed.2025.11.010

2. Bergler T, Hutchinson JA. Tools for Predicting Kidney Transplant Outcomes. Transplantation. 2017;101(9):1958-1959. doi:https://doi.org/10.1097/tp.0000000000001891

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