The Accuracy of Nonstandardized MELD/PELD Score Exceptions in the Pediatric Liver Allocation System

Area of Science:

• Hepatology
• Transplant Surgery
• Pediatric Gastroenterology

Background:

• Over half of pediatric liver transplant candidates in the U.S. receive score exceptions.
• These exceptions increase priority on the waitlist, potentially above their actual mortality risk.
• The accuracy of these "nonstandardized" exceptions in reflecting true pretransplant mortality risk is questioned.

Purpose of the Study:

• To determine if MELD/PELD exceptions accurately reflect pretransplant mortality risk in pediatric liver failure patients.
• To compare the predictive accuracy of laboratory MELD/PELD scores versus allocation MELD/PELD scores with exceptions.
• To assess the impact of the National Liver Review Board on exception rates.

Main Methods:

• Analysis of Scientific Registry of Transplant Recipients data for pediatric candidates (<18 years) with chronic liver failure.
• Use of mixed-effects Cox proportional hazards models to estimate pretransplant mortality.
• Comparison of laboratory MELD/PELD and allocation MELD/PELD performance using concordance statistics.

Main Results:

• Candidates prioritized by laboratory MELD/PELD had a significantly higher mortality risk (HR 8.69) than those with exception-based scores.
• Laboratory MELD/PELD scores were more accurate predictors of mortality (c-index 0.843) than allocation MELD/PELD scores (c-index 0.763).
• The proportion of patients with active exceptions decreased significantly post-National Liver Review Board implementation (67.4% vs. 43.4%).

Conclusions:

• Nonstandardized exceptions negatively impact the accurate ranking of pediatric liver failure candidates.
• Current exception policies may not adequately represent true pretransplant mortality risk.
• The National Liver Review Board has reduced the prevalence of active exceptions at transplant.