What is a MELD score?
MELD score or Model for End-stage liver disease is a scoring system used to assess the severity of chronic liver disease. Liver disease is defined as being chronic when it is present in a patient for a duration of more than six months. It is a prognostic model which is used to determine the severity and extent of liver disease in order to make decisions regarding specialist medical interventions such as specific medical treatments and or liver transplantation.
Components of a MELD score
This type of calculator relies solely on the use of laboratory values of the following three components to predict survival in a patient of chronic liver disease:
- Serum bilirubin: This measures liver function by gaging its function levels of bile production and excretion.
- Serum creatinine: this is a key indicator of kidney function. Impaired kidney function can be a consequence of liver disease, for example in hepato-renal syndrome.
- International normalized ratio for prothrombin time (PT): This can determine the liver’s ability to produce blood clotting factors.
This score is based on a numerical scale ranging from values of 6 (less seriously ill) to 40 (severely affected). It can be used for transplant candidates who are 12 years or older in age. It can be used to predict a value of how urgently the individual needs a transplant within duration of the next three months.
Importance of this scoring system
This scoring system helps the treating specialist make many critical decisions concerning welfare and care of a chronic liver disease sufferer. An increasing score value is considered to show a deteriorating and progressively worsening liver dysfunction. It also predicts the three-month mortality risk. Because of its accuracy in predicting the short-term survival in such patients, this score is effectively implemented in various decisions by the transplant community to prioritize patients awaiting a liver transplant.
The Score Formula
The MELD Score currently used by United Network for Organ Sharing (UNOS) to prioritize transplant organ follows the following formula:
MELD = 3.8[Ln serum bilirubin (mg/dL)] + 11.2[Ln INR] + 9.6[Ln serum creatinine (mg/dL)] + 6.4
Where, Ln is a natural algorithm
UNOS has also made a few modifications to this score. These include:
- If the patient has been on dialysis within the past 7 days, a creatinine value of 4.0 must be used
- Any value that is below one, is given the value of 1.
For example, if bilirubin’s value is 0.7, it is considered to be 1 instead. This is to prevent negative values. As a natural algorithm of the value is used, the natural algorithm of 1 is 0 so any value below 1 might give a negative value.
How does this score predict mortality?
There is a general key of how this score can be interpreted within a hospital setting. An estimated 3-month mortality is predicted with the help of the scoring value.
- A score of 40 or more predicts a 71.3% mortality
- A score between 30 and 39 predicts a 52.6% mortality
- A score between 20 and 29 predicts a 19.6% mortality
- A score between 10 and 19 predicts a 6.0% mortality
- A score below 9 and 1.9% mortality
Special case exemptions to MELD score
There is one special exemption to this method of survival prediction in chronic liver disease mentioned above. This includes a category of seriously ill patients known as status 1.
Less than one percent of liver transplant patients lie in this category.
This category includes patients who have an acute liver failure. This liver failure is sudden in onset and severe in intensity. This causes these individuals to have a life expectancy of a few hours to days if a timely transplant is not performed. Other than this all other patients who are above the age of 12 years are categorized by the MELD scoring system.
Patients who are under the age of 12 years are categorized by another scoring system. This is known as Pediatric End-stage Liver Disease (PELD) scoring system. This scoring system will use different factors according to the growth and developmental needs of the child.
Fluctuation in the value of the MELD Score
The value of this score does not stay constant throughout the patient’s lifetime. There may be fluctuations where the score may go up and down based on the status of the liver disease. This is why patients who are on the transplant list get their scores assessed repeatedly. This ensures that only these patients receive a donor liver who are in the greatest need at that time as assessed by the MELD score.