MELD-Na Score Calculator — Liver Transplant Priority

About

The MELD-Na (Model for End-Stage Liver Disease-Sodium) score was adopted by UNOS (United Network for Organ Sharing) in January 2016 as the standard scoring system for liver transplant organ allocation, replacing the traditional MELD score. It incorporates serum sodium as an additional variable because hyponatremia (low serum sodium) is an independent predictor of waitlist mortality in patients with cirrhosis and portal hypertension. The score ranges from 6 to 40, with higher scores indicating greater disease severity and mortality risk. Serum sodium is capped between 120 and 137 mEq/L — values below 120 are set to 120, and values above 137 are set to 137. The MELD-Na formula corrects the base MELD score upward for patients with hyponatremia, giving appropriate additional allocation priority to these higher-risk patients. Studies have shown that MELD-Na improves 3-month mortality prediction compared to MELD alone, with a c-statistic of 0.85 versus 0.83 for MELD, and more accurately identifies patients with the highest waitlist mortality risk.

Formula

MELD-Na = MELD + 1.32 × (137 - Na) - 0.033 × MELD × (137 - Na)

The MELD-Na score is calculated by first obtaining the standard MELD score using bilirubin, INR, and creatinine (with the dialysis rule: creatinine is set to 4.0 if the patient has had hemodialysis ≥2 times in the past 7 days or 24 hours of CVVHD). All three lab values are floored at 0.1 to avoid undefined logarithms. The standard MELD equation is: MELD = 3.78 × ln(bilirubin) + 11.2 × ln(INR) + 9.57 × ln(creatinine) + 6.43. The result is rounded to the nearest integer and capped at 6-40. Next, serum sodium is obtained and capped between 120 and 137 mEq/L: values below 120 are set to 120, and values above 137 are set to 137. The correction formula is: MELD-Na = MELD + 1.32 × (137 - Na) - 0.033 × MELD × (137 - Na). The first term adds a direct benefit proportional to the sodium deficit (1.32 points per mEq/L below 137). The second term subtracts a small adjustment proportional to the product of MELD and sodium deficit, preventing excessive correction in patients with both high MELD and very low sodium. The result is rounded to the nearest integer and capped at 6-40. A MELD-Na ≥21 is the optimal threshold for identifying patients with >15% 3-month mortality. Each 1-point increase in MELD-Na corresponds to approximately 1% increase in 3-month mortality risk, though this relationship is non-linear and accelerates at scores >25.

Score Interpretation

The MELD-Na score represents a significant improvement over the traditional MELD score for liver transplant allocation. Hyponatremia, defined as serum sodium <135 mEq/L, occurs in approximately 30% of patients with decompensated cirrhosis and is independently associated with increased waitlist mortality, hepatic encephalopathy, and spontaneous bacterial peritonitis. By incorporating sodium, MELD-Na more accurately identifies patients with the highest short-term mortality risk. Key clinical applications: (1) UNOS liver transplant allocation since 2016 — all patients on the US transplant waiting list are prioritized by MELD-Na. (2) Predicting 3-month waitlist mortality — MELD-Na has a c-statistic of 0.85, superior to MELD at 0.83. (3) Identifying patients who benefit most from early transplant listing — MELD-Na ≥21 identifies patients with >15% 3-month mortality. (4) Prognostic stratification in acute decompensation and acute-on-chronic liver failure (ACLF). Studies have shown that the sodium correction disproportionately benefits patients with low MELD but significant hyponatremia, who would be under-prioritized by traditional MELD. The implementation of MELD-Na-based allocation by UNOS was associated with a 7% reduction in waitlist mortality in the first year alone. MELD-Na has been validated across diverse etiologies of liver disease including alcohol-related liver disease, NASH, viral hepatitis, and autoimmune liver disease.

Reference Ranges