What is the role of the Model for End-Stage Liver Disease (MELD) score in determining priority for liver transplant candidates?

Role of MELD Score in Liver Transplant Prioritization

The MELD score is the primary tool for determining liver transplant priority, predicting short-term mortality risk and guiding organ allocation based on objective laboratory tests including bilirubin, INR, and creatinine. 1, 2

MELD Score Fundamentals

• MELD score calculation uses the formula: 3.78 × log(bilirubin) + 11.2 × log(INR) + 9.6 × log(creatinine) + 6.4 2
• Originally developed to predict outcomes in TIPS patients, now validated for predicting 3-month mortality in end-stage liver disease 1, 3
• Higher scores correlate with increased mortality risk without transplantation:
  • MELD 6-9: 1.9% mortality risk
  • MELD 10-19: 6% mortality risk
  • MELD 20-29: 19.6% mortality risk
  • MELD 30-39: 52.6% mortality risk
  • MELD 40+: 71.3% mortality risk 2

Transplant Listing Thresholds

• A MELD score ≥15 is recommended for listing patients with end-stage liver disease 1, 2
• Patients with MELD <14 have better 1-year survival without transplantation than with it 1
• Early referral recommended when MELD >10 or first major complication occurs 2
• Urgent referral necessary for acute liver failure or rapid decompensation 2

MELD Exceptions and Limitations

MELD has several recognized limitations that require adjustments in organ allocation:

1. Conditions not adequately captured by MELD:

   • Hepatocellular carcinoma (HCC)
   • Pulmonary complications of cirrhosis
   • Hepatic encephalopathy
   • Amyloidosis
   • Primary hyperoxaluria 1

2. Proposed MELD modifications to improve predictive value:

   • MELD-Na (includes serum sodium)
   • Integrated MELD (includes sodium and age)
   • Delta MELD (change over time)
   • MELD 3.0 (includes sex, albumin, and revised weights for components) 1, 2

3. Special considerations:

   • Patients with severe hepatic encephalopathy (grade 3-4) and MELD 30-34 have similar 90-day waitlist mortality as patients with MELD ≥35 without severe encephalopathy 4
   • Female patients may have worse outcomes than males with the same MELD score 2

Impact on Post-Transplant Outcomes

• MELD scores correlate inversely with post-transplant survival 5
• Very high MELD scores (>25) are associated with poorer post-transplant outcomes, with maximum impact during the first year 5
• In very sick patients with MELD >30, the risk of mortality and morbidity after transplantation must be carefully assessed 1

Practical Application in Organ Allocation

• MELD score drives graft allocation in many countries 1
• Final allocation decisions typically consider multiple factors beyond MELD:
  • Donor-recipient matching
  • Local/regional priorities
  • Expert assessment for MELD exceptions 1
• For HCC patients, additional points are added to the laboratory MELD based on:
  • Tumor characteristics (size, number of nodules)
  • Alpha-fetoprotein levels
  • Waiting time
  • Response to downstaging procedures 1

Risk Stratification for Extremely Ill Patients

• Status 1A patients (acute liver failure) are traditionally prioritized over high MELD patients
• Risk factors for waitlist mortality in MELD ≥40 patients include:
  • MELD scores ≥45
  • Age
  • Sex
  • Race
  • Life support requirements
  • Encephalopathy 6

Monitoring and Reassessment

• MELD scores tend to increase over time rather than decrease 7
• Serial MELD calculations are essential for tracking disease progression and prioritization 2
• Creatinine is the most stable MELD component (ICC: 0.89), while bilirubin and INR show greater variability 7

The MELD score has revolutionized liver allocation by providing an objective measure of disease severity, ensuring that the sickest patients receive priority for this scarce resource while balancing the need for good post-transplant outcomes.