How is the Model for End-Stage Liver Disease (MELD) score calculated for liver cirrhosis?

Calculation of MELD Score for Liver Cirrhosis

The Model for End-Stage Liver Disease (MELD) score is calculated using the formula: MELD = 3.78 × ln[serum bilirubin (mg/dL)] + 11.2 × ln[INR] + 9.57 × ln[serum creatinine (mg/dL)] + 6.43.

Components of the MELD Score

The MELD score incorporates three objective laboratory values:

1. Serum bilirubin (mg/dL) - measures liver's ability to excrete bile
2. International Normalized Ratio (INR) - measures liver's synthetic function
3. Serum creatinine (mg/dL) - measures kidney function

Important Calculation Rules

• The formula uses the natural logarithm (ln) of each laboratory value
• Laboratory values less than 1.0 are set to 1.0 to avoid negative values
• Serum creatinine is capped at 4.0 mg/dL
• For patients who received dialysis twice within the last week, creatinine is automatically set to 4.0 mg/dL
• The final score is rounded to the nearest whole number
• The score ranges from 6 (less ill) to 40 (gravely ill)

Clinical Significance and Interpretation

The MELD score was originally developed to assess short-term prognosis in patients undergoing transjugular intrahepatic portosystemic shunts (TIPS) 1. It has since become the standard tool for:

• Prioritizing patients on liver transplantation waiting lists
• Predicting 3-month mortality in patients with end-stage liver disease
• Risk-stratifying cirrhotic patients before surgical procedures

MELD score correlates with mortality risk as follows:

• Score <10: 1.9% 3-month mortality
• Score 10-19: 6% 3-month mortality
• Score 20-29: 19.6% 3-month mortality
• Score 30-39: 52.6% 3-month mortality
• Score ≥40: 71.3% 3-month mortality

Advantages Over Other Scoring Systems

The MELD score offers several advantages over the Child-Turcotte-Pugh (CTP) score:

• Uses only objective laboratory parameters
• Provides a continuous scale rather than categorical classification
• Includes assessment of renal function, which is a critical prognostic factor
• Better predicts short-term mortality in patients with cirrhosis

Clinical Applications Beyond Transplantation

The MELD score is valuable for:

• Predicting perioperative mortality in cirrhotic patients undergoing non-transplant surgery 2
• Assessing prognosis in alcoholic hepatitis when MELD ≥18 indicates poor prognosis 1
• Evaluating candidacy for hepatic resection in cirrhotic patients with hepatocellular carcinoma 3

Limitations and Pitfalls

• May underestimate mortality in patients with acute-on-chronic liver failure due to extrahepatic organ failures 1
• Does not account for complications of portal hypertension (varices, ascites) 1
• May disadvantage patients with viral cirrhosis compared to alcoholic cirrhosis at the same MELD score 4
• Serum creatinine can be an unreliable marker of renal dysfunction in cirrhotic patients 1

Modified Versions

Several variations have been developed to improve prognostic accuracy:

1. MELD-Na: Incorporates serum sodium to account for hyponatremia
2. MELD-lactate (MELD-LA): Adds serum lactate, which improves prediction of in-hospital mortality 1
3. Delta MELD: Evaluates the change in MELD score over time

When to Refer for Liver Transplantation

According to AASLD guidelines, patients with cirrhosis should be referred for transplantation when:

• MELD score >10 with evidence of hepatic dysfunction
• CTP score >7
• First major complication (ascites, variceal bleeding, or hepatic encephalopathy) 1

Remember that sequential assessment of MELD scores over time provides better prognostic information than a single measurement, particularly in patients with acute-on-chronic liver failure 1.