hannesill/m4/meld-score

MELD Score Calculation

The Model for End-Stage Liver Disease (MELD) score predicts 3-month mortality in patients with liver disease. Originally developed for TIPS procedure prognostication, it is now the primary organ allocation criterion for liver transplantation in the US. The MELD-Na variant incorporates serum sodium for improved prediction.

When to Use This Skill

• Liver disease severity assessment
• Transplant prioritization research
• Hepatology outcome studies
• Cirrhosis prognosis evaluation

Score Components

MELD uses 4 laboratory values with logarithmic transformations:

Calculation Steps

1. Component scores (all values floored at 1.0 for logarithm):

• Creatinine: 0.957 × ln(max(Cr, 1)) — capped at Cr=4 if RRT or Cr > 4
• Bilirubin: 0.378 × ln(max(Bili, 1))
• INR: 1.120 × ln(max(INR, 1)) + 0.643

1. MELD Initial: round(Cr_score + Bili_score + INR_score, 1) × 10

• Capped at 40 if sum > 4

1. Sodium adjustment (MELD-Na, only if MELD Initial > 11):

• Sodium score: 137 - max(min(Na, 137), 125)
• MELD = MELD_Initial + 1.32 × Na_score - 0.033 × MELD_Initial × Na_score
• If MELD Initial ≤ 11: MELD = MELD Initial (no sodium adjustment)

Critical Implementation Notes

1. Creatinine Cap: Patients on renal replacement therapy (RRT/dialysis) OR with creatinine > 4.0 are scored as creatinine = 4.0. This prevents extreme renal failure from dominating the score.

1. INR Constant Term: Unlike other components, INR scoring adds a constant 0.643 even when INR = 1 (ln(1) = 0). This means the minimum contribution from INR is always 0.643.

1. Sodium Conditional: The sodium adjustment is ONLY applied when MELD Initial > 11. Below this threshold, mild liver disease is not affected by hyponatremia.

1. Score Range: Theoretical minimum ~6 (all normal values), maximum 40 (hard cap).

1. RRT Detection: In MIMIC-IV, dialysis is detected from the first_day_rrt derived table, which checks for CRRT/IHD procedures in the first 24 hours.

1. Missing Lab Values: When a lab value is not available for a stay, the component defaults to its minimum contribution: ln(1) = 0. This means creatinine scores as 1.0, bilirubin scores as 1.0, INR scores as 1.0 (but still contributes the +0.643 constant), and sodium defaults to 137 (no adjustment). Include ALL ICU stays in the output, even those missing some or all lab values.

Pre-computed Table

MIMIC-IV provides a pre-computed MELD table:

SELECT
    stay_id,
    meld,
    meld_initial,
    rrt,
    creatinine_max,
    bilirubin_total_max,
    inr_max,
    sodium_min
FROM mimiciv_derived.meld;

Required Tables for Custom Calculation

• mimiciv_icu.icustays — ICU stay identifiers
• mimiciv_derived.first_day_lab — creatinine_max, bilirubin_total_max, inr_max, sodium_min
• mimiciv_derived.first_day_rrt — dialysis_present flag

References

• Kamath PS et al. "A model to predict survival in patients with end-stage liver disease." Hepatology. 2001;33(2):464-470.
• Kim WR et al. "Hyponatremia and mortality among patients on the liver-transplant waiting list." N Engl J Med. 2008;359(10):1018-1026.
• Biggins SW et al. "Evidence-based incorporation of serum sodium concentration into MELD." Gastroenterology. 2006;130(6):1652-1660.