Understanding the MELD Score
The MELD scoring system ranks adult patients on liver transplant waiting lists from 1 (least urgent) to 40 (most critical). Rather than allocating organs by waiting time alone, this standardised metric ensures organs go to patients with the highest mortality risk in the next 90 days. The score reflects disease severity across multiple organ systems—liver, kidneys, and clotting cascade.
Two versions exist: the original formula (used internationally) and the 2016 update (adopted by United Network for Organ Sharing in the US), which accounts for serum sodium concentration. Sodium adjustment captures the impact of hyponatraemia on prognosis more accurately than kidney function markers alone.
MELD calculations are typically performed when:
- A patient is evaluated for transplant candidacy
- Monitoring liver disease progression during treatment
- Assessing perioperative risk in cirrhotic patients
MELD Score Calculation
Both formulas use natural logarithm (ln) of three key blood values. The original formula produces a score capped between 1 and 40, while the 2016 modification adjusts this based on serum sodium concentration.
MELD Score (Original) = max(1, min(40,
10 × [(0.957 × ln(Creatinine)) + (0.378 × ln(Bilirubin)) + (1.12 × ln(INR))] + 6.43))
MELD Score (2016) = MELD Score + 1.32 × (137 − Sodium)
− 0.033 × MELD Score × (137 − Sodium)
Creatinine— Serum creatinine in mg/dL; use 4.0 if dialysed twice weekly or receiving CVVHDBilirubin— Total serum bilirubin in mg/dLINR— International normalised ratio (prothrombin time ratio)Sodium— Serum sodium in mmol/L; capped between 125 and 137 in the 2016 formula
Laboratory Values and Clinical Context
Accurate MELD calculation requires recent laboratory results, ideally within the past week. Each input represents a specific organ system vulnerability:
Creatinine reflects glomerular filtration rate; elevations signal acute kidney injury or chronic kidney disease superimposed on liver failure. If a patient has undergone twice-weekly dialysis or continuous veno-venous haemodiafiltration within 24 hours, input 4.0 mg/dL regardless of measured value.
Bilirubin (total, in mg/dL) indicates hepatic synthetic dysfunction and cholestasis. Conjugated hyperbilirubinaemia suggests more severe liver injury.
INR (prothrombin time ratio) measures clotting factor production—a sensitive marker of liver synthetic capacity. Values above 1.5 usually indicate clinically significant coagulopathy.
Sodium (mmol/L or mEq/L) reflects portal hypertension severity and neurohormonal activation. Hyponatraemia below 125 is capped in calculations; hypernatraemia above 137 does not improve the score.
Clinical Considerations and Pitfalls
Accurate interpretation requires awareness of score limitations and clinical context.
- Score caps and floor values — The MELD score is mathematically constrained between 1 and 40. Extremely elevated lab values do not push the score higher; conversely, any calculated value below 1 is reported as 1. This ceiling prevents distortion from single outlier results.
- Dialysis and creatinine capping — Patients on renal replacement therapy pose a diagnostic challenge—their measured creatinine may not reflect true kidney function. Always use the 4.0 mg/dL imputed value for patients dialysed twice weekly or more, even if serum creatinine appears lower.
- Sodium adjustment timing — The 2016 formula benefits hyponatraemic patients most; however, sodium correction with hypertonic saline or fluid restriction takes days to weeks. Do not repeat MELD calculations more than weekly unless a major clinical event (sepsis, bleeding) has occurred.
- Extra-hepatic causes of derangement — Renal failure from sepsis, volume depletion, or medications can artificially elevate MELD scores in patients with milder liver disease. Conversely, stable cirrhotic patients with accidental laboratory errors (e.g., specimen haemolysis falsely raising bilirubin) may be misclassified. Always corroborate scores with clinical assessment and imaging.
Mortality Risk Stratification
The MELD score predicts 90-day mortality with good calibration across the range:
- MELD ≤ 9: 1.9% mortality risk—typically compensated disease or early decompensation
- MELD 10–19: 6.0% mortality risk—moderate decompensation
- MELD 20–29: 19.6% mortality risk—severe disease warranting closer monitoring
- MELD 30–39: 52.6% mortality risk—urgent transplant consideration
- MELD 40: 71.3% mortality risk—highest priority; transplant within days if possible
These thresholds guide clinical decisions: patients with MELD scores above 15 are typically listed for transplant, while those below 10 usually do not meet urgency criteria unless they have hepatocellular carcinoma or other complications.