MELD Labs: The Three Core Laboratory Values
MELD (Model for End-Stage Liver Disease) labs consist of three objective laboratory parameters: serum bilirubin, INR (International Normalized Ratio), and serum creatinine. 1
The Three Laboratory Components
The MELD score incorporates exactly three blood tests that have been identified as the best predictors of 3-month mortality in patients with end-stage liver disease: 2
- Serum bilirubin (measured in mg/dL) - reflects hepatic synthetic function and is weighted as 3.8 × log(bilirubin) in the MELD formula 2
- INR (International Normalized Ratio) - measures coagulation function and prothrombin time, weighted as 11.2 × log(INR) in the calculation 2, 3
- Serum creatinine (measured in mg/dL) - represents renal function and is weighted as 9.6 × log(creatinine) in the formula 2
The MELD Score Calculation
These three laboratory values are combined into a logarithmic formula that produces a continuous numerical scale from 6 to 40, with higher scores indicating greater disease severity and mortality risk. 2, 4 The score correlates with estimated 3-month survival rates ranging from 90% (MELD 6) to 7% (MELD 40). 2
Enhanced Versions: MELD-Na and MELD 3.0
MELD-Na adds a fourth laboratory value to improve mortality prediction: 1
- Serum sodium - hyponatremia is an independent predictor of death in cirrhotic patients with ascites, particularly when sodium levels fall below 130 mmol/L 1
- MELD-Na is now the recommended system by the American Association for the Study of Liver Diseases for liver transplant allocation in the United States 1
MELD 3.0 (the newest version) incorporates: 5
- Serum albumin - added to improve prediction accuracy and reduce gender disparities 5
- Patient sex as a variable 5
- Modified creatinine upper bound at 3.0 mg/dL (rather than 4.0 mg/dL) 5
Critical Clinical Caveats
Creatinine limitations: Serum creatinine can be unreliable in cirrhotic patients—it overestimates renal dysfunction in patients with sarcopenia (low muscle mass) and underestimates it in those with fluid overload. 1 Patients on renal replacement therapy receive a maximum creatinine value of 4.0 mg/dL in the standard MELD calculation. 1
INR reliability: The INR used in MELD is calibrated for patients on warfarin, yet it performs excellently in liver disease with a c-statistic of approximately 0.8 for mortality prediction. 3
Primary Clinical Application
The MELD score is calculated using these labs to prioritize liver transplant allocation based on objective mortality risk. 1 A MELD score ≥15 is the established threshold for transplant listing, as patients with MELD ≤14 have better 1-year survival without transplantation than with it. 1, 2