Pediatric Risk to OHT (PRO) Score: Insights from UNOS Waitlist Mortality Findings

Abstract

<h3>Purpose</h3> Waitlisted pediatric heart transplant candidates have the highest mortality rate amongst solid organ transplants. The current criteria in the United States provides equal weight to a patient's medical severity and waitlist time. A risk score much like the Model for End Stage Liver Disease (MELD) score utilized for patients awaiting liver transplant would incorporate a candidate's unique risk factors to predict mortality on the waitlist and optimize organ allocation to the sickest awaiting transplantation. <h3>Methods</h3> Utilizing the United Network for Organ Sharing (UNOS) database, a total of 5557 patients aged 0-18 years old on the waitlist for a single, first time, heart transplant from January 2010-June 2019 were evaluated. A univariate analysis was performed on two-thirds (N=3705) of these patients to derive the factors most associated with waitlist mortality or delisting within 1 year. Those with a p-value < 0.2 underwent a multivariate analysis and the resulting factors were used to build a prediction model using the Fine-Grey model analysis. This predictive scoring model was validated on the remaining one-third of the patients (N=1852). <h3>Results</h3> The Pediatric Risk to OHT (PRO) scoring model utilized the following unique patient variables: blood type, diagnosis of congenital heart disease, weight, ventilator support, inotropic support, extracorporeal membrane oxygenation (ECMO) status, creatinine level, and region (Figure 1A). A higher score indicates an increased risk of mortality. The PRO score had a predictive strength of 0.745 as measured by Area Under the ROC curve at 1 year (Figure 1B). The derivation group had a PRO score mean of 1.35 (standard deviation 0.88) and median of 1.39; the validation group had a comparable PRO score mean of 1.33 (standard deviation of 0.90) and median of 1.35. <h3>Conclusion</h3> The PRO score is an improved predictive model to better assess the mortality for patients awaiting heart transplant. With prospective application, this study aims to improve allocation of a limited resource.