The Model for End-Stage Liver Disease (MELD) score is a standardized numerical system used by medical professionals to objectively assess the severity of chronic liver disease in adults. This score provides a quantifiable measure of how poorly a patient’s liver and associated organ systems are functioning. The primary purpose of the MELD system is to predict a patient’s short-term survival outlook, specifically the risk of mortality within the next 90 days. By converting complex laboratory results into a single number, the MELD score allows healthcare providers to monitor disease progression and make informed decisions regarding treatment and intervention.
Defining the MELD Score: The Baseline
The MELD score is calculated on a continuous scale that spans from a minimum of 6 to a maximum of 40. Lower numbers indicate better liver health, and higher numbers signify more severe disease. The lowest possible score, 6, is the operational baseline for this system and represents a healthy or near-healthy level of liver function. This minimum value is considered the “normal” result within the MELD scoring context. The MELD score is a dynamic measure that can change as a patient’s condition improves or worsens, necessitating regular recalculation to accurately reflect their current state.
How the MELD Score is Calculated
The MELD score is derived from a mathematical formula that incorporates the results of several routine blood tests, providing an objective measure of both liver and kidney function.
Core Components
The calculation includes four primary laboratory values:
- International Normalized Ratio (INR): Assesses the liver’s ability to produce clotting factors. A prolonged clotting time leads to a higher MELD score.
- Serum Total Bilirubin: Elevated levels indicate the liver is failing to excrete bile properly.
- Serum Creatinine: Measures how effectively the kidneys are filtering the blood. Kidney dysfunction often occurs as liver disease progresses.
- Serum Sodium (MELD-Na): Included to increase prediction accuracy, especially in patients with fluid imbalances. Low sodium levels are often a sign of severe fluid retention and advanced liver disease.
The inclusion of these four objective laboratory values ensures the final score is based on precise, measurable biological indicators.
Interpreting Score Ranges and Prognosis
The numerical outcome of the MELD calculation is directly linked to the patient’s prognosis, with higher scores predicting a significantly greater risk of death within a 90-day period.
MELD Score Mortality Risk (90 Days)
- Score 9 or less: The predicted 90-day mortality risk is approximately 1.9 percent. This low-range score suggests the short-term outlook is relatively stable.
- Score 10 to 19: The estimated 90-day risk of mortality increases to about 6 percent.
- Score 20 to 29: The prognosis worsens considerably, with the predicted short-term mortality risk climbing to nearly 20 percent. This signals a more urgent medical situation.
- Score 30 to 39: The predicted 90-day mortality risk surpasses 50 percent. Patients are gravely ill and require immediate intervention.
- Score 40 or higher: The risk of death within 90 days can exceed 70 percent, underscoring the severity of decompensated liver failure.
MELD’s Role in Organ Allocation
Beyond predicting survival, the MELD score serves a fundamental administrative function in the United States by governing the allocation of deceased-donor livers. The system was adopted by the Organ Procurement and Transplantation Network (OPTN) and the United Network for Organ Sharing (UNOS) to ensure ethical and equitable organ distribution. This policy ensures that the sickest patients—those with the highest MELD scores—are prioritized on the liver transplant waitlist. The MELD model uses an objective and verifiable scoring system based on medical urgency, moving away from subjective criteria. Continuous re-evaluation of a patient’s health status ensures that the limited supply of donor organs is directed toward those most likely to die without a transplant.