What laboratory values are required to calculate a patient's MELD (Model for End-Stage Liver Disease) score and how is it calculated?

How to Calculate a MELD Score

The MELD (Model for End-Stage Liver Disease) score is calculated using three laboratory values: serum bilirubin, serum creatinine, and INR (International Normalized Ratio). The formula is:

MELD Score = 3.78 × log(bilirubin in mg/dL) + 11.2 × log(INR) + 9.6 × log(creatinine mg/dL) + 6.4 1

Required Laboratory Values

To calculate a patient's MELD score, you need:

1. Serum bilirubin (measured in mg/dL)
2. International Normalized Ratio (INR) of prothrombin time
3. Serum creatinine (measured in mg/dL)

Calculation Process

1. Take the natural logarithm (ln) of each laboratory value
2. Multiply each logarithm by its respective coefficient:
   • Bilirubin: multiply by 3.78
   • INR: multiply by 11.2
   • Creatinine: multiply by 9.6
3. Add these products together
4. Add the constant 6.4
5. Round to the nearest whole number

Important Considerations

• Laboratory methodology matters: Different laboratory methods can yield significantly different MELD scores. Studies have shown that INR measurements can vary by up to 26% between laboratories, potentially changing a patient's MELD score by several points 2.

• Parameter adjustments: For accurate calculation, the following rules apply:

  • If any value is less than 1.0, use 1.0 instead
  • Maximum serum creatinine value is capped at 4.0 mg/dL
  • For patients who have had dialysis twice within the last week, creatinine should be set to 4.0 mg/dL 1

• Interfering factors: Be aware of factors that can affect MELD parameters:

  • Oral anticoagulants affect INR
  • Renal insufficiency affects creatinine
  • High bilirubin levels can interfere with creatinine measurement 3, 4

Clinical Significance

The MELD score ranges from 6 to 40, with higher scores indicating more severe disease and higher mortality risk:

• MELD ≥ 18 indicates poor prognosis in alcoholic hepatitis 1
• MELD ≥ 15 corresponds approximately to Child-Pugh class C 1, 4
• MELD 10-15 corresponds approximately to Child-Pugh class B 4
• MELD < 9 is associated with lower perioperative mortality in patients with cirrhosis undergoing hepatic resection 5

Online Calculators

For convenience, validated online calculators are available:

• Mayo Clinic MELD calculator: www.mayoclinic.org/meld/mayomodel7.html 1

Pitfalls to Avoid

• Laboratory variability: Different laboratory methodologies can significantly affect MELD scores. This is particularly important for transplant prioritization 2, 3.

• Bilirubin interference: High bilirubin levels can interfere with creatinine measurement, potentially causing up to 7-point variations in MELD scores when bilirubin exceeds 400 μmol/L 3.

• Non-liver causes of abnormal values: The MELD score may be artificially elevated in patients with renal failure or those taking anticoagulants, which doesn't necessarily reflect liver disease severity 4, 6.

The MELD score has become the standard for prioritizing patients for liver transplantation and is also valuable for predicting outcomes in various clinical scenarios involving liver disease 1, 6.