MELD Score

# Overview
The Model for End-Stage Liver Disease (MELD) is a reliable measure of mortality risk in patients with end-stage liver disease. It is used as a disease severity index to help prioritize allocation of organs for transplant.  The new system, known as the Model for End-Stage Liver Disease (MELD) score, leaves no room for subjective criteria favoritism or hospital-shopping, as it is based on a mathematical equation.  The equation seeks to calculate a patients likelihood of dying within three months from their liver disease.  In other words under the MELD scoring system - the sickest patient gets the liver transplant. It is more recent than the Child-Pugh score.

# Historical Perspective
This model was derived from a heterogeneous group of patients at 4 medical centers in the United States and validated in an independent data set from the Netherlands.
The original version of the MELD scale as developed by investigators at Mayo Clinic.  It was initially described by Kamath et al in 2001 and modified by Wiesner et al, also in 2001.  A number of modification have been made by UNOS (United Network for Organ Sharing) to the model for its implementation in organ allocation for liver transplantation.  The Model for End-Stage Liver Disease (MELD) score has been used by the Organ Procurement and Transplantation Network (OPTN) since February 2002 as the basis for allocation of deceased donor livers for transplantation among adults in the United States.

# Calculation of MELD Score
The MELD Calculator is a utility that allows you to enter hypothetical or actual parameters and calculate a MELD score for an individual patient.  The MELD/PELD Calculator uses the specific formulas approved by the OPTN/UNOS Board of Directors and used for the allocation of livers by the OPTN match system.  The MELD score calculation uses-
- Serum creatinine (mg/dl) *
- Bilirubin (mg/dl)
- INR
For candidates on dialysis, defined as having 2 or more dialysis treatments within the prior week; or candidates who have received 24 hours of CVVHD (Continuous Veno-venous Hemodialysis) within the prior week, will have their serum creatinine level automatically set to 4.0 mg/dl.  The MELD Calculator is used for candidates who are 12 years and older.

# MELD Formula
The MELD (Model for End Stage Liver Disease) is a more objective prognostic score, requiring however a calculation software.  The MELD score is calculated using the following formula
- MELD Score = 0.957 x Loge(creatinine mg/dL) + 0.378 x Loge(bilirubin mg/dL) + 1.120 x Loge(INR)+ 0.6431
Multiply the score by 10 and round to the nearest whole number. Laboratory values less than 1.0 are set to 1.0 for the purposes of the MELD score calculation.
-r MELD score= 3.8 + 11.2 + 9.6 + 6.4 
Caveats with the score include:
- The maximum score given for MELD is 40.  All values higher than 40 are given a score of 40
- If the patient has been dialyzed twice within the last 7 days, then the value for serum creatinine used should be 4.0
- Any value less than one is given a value of 1 (i.e. if bilirubin is 0.8, a value of 1.0 is used).

## Mortality Outcome
In interpreting the MELD Score in hospitalized patients, the 3 month mortality is: 
- 40 or more  71.3% mortality
- 3039  52.6% mortality
- 2029  19.6% mortality
- 1019  6.0% mortality
- <9  1.9% mortality

# The MELD caclulators
A variety of calculators which are specific to a particular clinical scenerio are as follows --
- The above mentioned UNOS MELD score has laboratory values of INR, total bilirubin and serum creatinine that are <1.0 are set to 1.0. It is used while setting priority for allocating deceased donor organs for liver transplantation.
- The first MELD score does not use upper or lower limits for laboratory values. Hence, they could have negative values to positive infinity. These are not used for allocation purposes while considering liver transplantation.
- A MELD score calculator to predict 90-day mortality in patients with alcoholic hepatitis 
- A MELD score calculator for predicting postoperative mortality risk in patients with cirrhosis. This calculator is based upon the first published MELD score, thus the etiology of liver disease is required for the calculation 
- A MELD-Na calculator, which incorporates serum sodium into the model 

# Comparing Child-Pugh and MELD score
The limitations of Child-Pugh score are as follows-
- Its based on subjective parameters like ascites and encephalopathy. Not only do these criterias vary with observers but also they may be affected by interventions like diuretics etc.
- It has a "ceiling and floor" effect. Example- a serum albumin value of 2.8 versus 1.5 will be highly varied clinically but it is rewarded the same point on Child-Pugh.
- Laboratory to laboratory variations in albumin and prothrombin values.
The points where MELD definitely edges over Child-Pugh score are-
- It relies on few, readily available, objective variables.
- Applicable to diverse set of patients with liver disease.
- Identifies and distinguishes the various points of severity along the disease spectrum.
The points where MELD lags behind are -
- Like Child-Pugh score, it is not immune to laboratory variations in INR and creatinine values.
Studies have compared the accuracy of MELD versus the Child-Pugh score for predicting the survival of patients on liver transplant waiting list have shown an equivalence but not superiority. The objective criteria used in the MELD score have led to widespread adoption of MELD as an accurate mortality predictor in patients awaiting liver transplantation.

# Improving MELD score
The proposed modifications that are on way for MELD score are as follows--
- MELDNa   Serum sodium levels decrease in cirrhotic patients. One school of thought suggests that in the setting of hyponatremia, it would be advisable to include serum sodium levels in the MELD model. Improvement in accuracy of the MELD score has been noted in studies.
- Reweighting of MELD components  MELD formula is getting updated in its weightage being given to coefficients. The updated formula gives lower weightage to serum creatinine and INR and higher to bilirubin.