The United Network for Organ Sharing (UNOS), a non-profit charitable
organization, operates the Organ Procurement and Transplantation Network
(OPTN) under federal contract. On an ongoing basis, the OPTN/UNOS
evaluates new advances and research and adapts these into new policies to
best serve patients waiting for transplants.
As part of this process, the OPTN/UNOS developed a system for prioritizing
candidates waiting for liver transplants based on statistical formulas that are
very accurate for predicting who needs a liver transplant most urgently.
The MELD (Model for End Stage Liver Disease) is used for candidates age 12
and older and the PELD (Pediatric End Stage Liver Disease Model) is used
for patients age 11 and younger.
This document will explain the system and how it affects those needing a transplant.
What is MELD? How will it be used?The Model for End-Stage Liver Disease (MELD) is a numerical scale, ranging
from 6 (less ill) to 40 (gravely ill), used for liver transplant candidates age 12
and older. It gives each person a ‘score’ (number) based on how urgently he
or she needs a liver transplant within the next three months. The number is
calculated by a formula using three routine lab test results:
I bilirubin, which measures how effectively the liver excretes bile;
I INR (prothrombin time), which measures the liver’s ability to make blood
clotting factors; and
I creatinine, which measures kidney function. (Impaired kidney function is
often associated with severe liver disease.)
The only priority exception to MELD is a category known as Status 1. Status 1 patients
have acute (sudden and severe onset) liver failure and a life expectancy of
hours to a few days without a transplant. Less than one percent of liver
transplant candidates are in this category. All other liver candidates age 12
and older are prioritized by the MELD system.
A patient’s score may go up or down over time depending on the status of his
or her liver disease. Most candidates will have their MELD score assessed a
number of times while they are on the waiting list. This will help ensure that
donated livers go to the patients in greatest need at that moment.
美国器官移植共享网-一个非营利的慈善组织,在联邦体制下运行器官切取和移植方面的网络。在不断前进的基础之上,OPTN/UNOS对新的进展和研究进行了评价,使之适应新的政策,以便更好的为等待移植患者服务。作为此项计划的一部分,OPTN/UNOS提出了一种新系统,以便更好的对等待肝移植患者进行划分等级,该系统是建立在统计公式基础之上,可以非常精确的估计哪个患者更迫切需要肝移植。MELD(终末期肝病模型)用于年龄>=12岁的患者, PELD (小儿终末期肝病模型)用于年龄<=11岁患者。
什么是MELD?怎样使用MELD?
MELD是一个从6(轻微疾病)到40(严重疾病)变化的数字范围,用于年龄>=12岁的等待移植的患者,其在他或她在三个月内需要肝移植的迫切程度的基础上,给了每个人一个分数(数字)。这个数字是根据三个常规的实验室检查结果通过一个公式计算出来的:
胆红素:检查肝脏分泌胆汁的功能
国际标准化比率(凝血酶原时间):检查肝脏生成凝血因子的能力
肌酐:检查肾脏功能(与严重肝脏疾病相关的肾功能损害)
MELD唯一例外优先的是这种情况:这种该患者有急性肝衰(突发或起病严重),如果没有移植的话,其与其寿命只有几个小时到几天。仅仅有不到1%的患者属于这种情况。所有其他年龄>=12岁的患者是按照MELD系统进行评估的。
一个患者的分数可能会根据其肝脏疾病的状况升高或者降低。大部分等待肝移植患者,会对其进行多次MELD评分。这样可以确保供肝能够给与那些最需要的患者。
What is PELD? How does it differ from MELD?
Candidates age 11 and younger are placed in categories according to the
Pediatric End-stage Liver Disease (PELD) scoring system. Again there is a Status 1
category for highly urgent patients, representing about one percent of those
listed. All other candidates in this age range receive priority through PELD.
PELD is similar to MELD but uses some different factors to recognize the specific
growth and development needs of children. PELD scores may also range higher
or lower than the range of MELD scores. The measures used are as follows:
I bilirubin, which measures how effectively the liver excretes bile;
I INR (prothrombin time), which measures the liver’s ability to make blood
clotting factors;
I albumin, which measures the liver’s ability to maintain nutrition;
I growth failure; and
I whether the child is less than one year old.
As with MELD, a patient’s score may go up or down over time depending on
the status of his or her disease. Most candidates will have their PELD score
assessed a number of times while they are on the waiting list. This will help
ensure that donated livers go to the patients in greatest need at that moment.
What Led To the MELD/PELD System?
Until 2002, patients needing liver transplants were grouped into four medical
urgency categories. The categories were based on a scoring system that
included some laboratory test results and some symptoms of liver disease.
One concern with using symptoms in scoring was that different doctors might
interpret the severity of those symptoms in different ways. In addition, this
scoring system could not easily identify which patients had more severe liver
disease and were in greater need of a transplant.
Research showed that MELD and PELD accurately predict most liver patients’
short-term risk of death without a transplant. The MELD and PELD formulas
are simple, objective and verifiable, and yield consistent results whenever the
score is calculated.
OPTN/UNOS committees developed the liver policy based on MELD and
PELD, with key support from transplant patient/family advocates. It was
approved by the OPTN/UNOS Board of Directors in November 2001 and went
into effect in February 2002.
How are livers offered through MELD and PELD?
Livers are offered first to urgent and compatible patients in the donor’s local
area (often defined as a state or large metropolitan area), then to a larger region
of the country (the OPTN/UNOS has 11 allocation regions in the U.S.), then
nationwide. Because Status 1 candidates are most medically urgent, each liver
is first offered to local Status 1 candidates, then regional Status 1 candidates.
The sequence of offers after Status 1 patients depends on the donor’s age.
If the donor is younger than 18, after any Status 1s are considered the liver
would next be offered to candidates in the region age 11 or younger. The
organ would then be considered for local and then regional candidates with
a MELD of 15 or higher. Any patients age 12 to 17 would be considered
ahead of adult patients.
If the donor is 18 or older, the liver would be offered first to local and
regional Status 1 candidates. If not accepted for any of these patients, the
liver is then offered to candidates with a MELD/PELD score of 15 or higher,
first locally and then regionally.
If the liver is not matched to any candidates with a MELD/PELD of 15 or
higher, it may then be considered for local, then regional candidates with a
MELD/PELD of 14 or less. Finally the liver would be offered for any compatible
candidates nationwide, beginning with Status 1 candidates and then to
those with the highest MELD/PELD scores.
How is waiting time counted in the system?
Various studies report that waiting time is a poor indicator of how urgently
a patient needs a liver transplant. This is because some patients are listed
for a transplant very early in their disease, while others are listed only when
they become much sicker.
Under the MELD/PELD system with a wide range of scores, waiting time is
not often used to break ties. Waiting time will only determine who comes
first when there are two or more patients with the same blood type and the
same MELD or PELD score.
If a patient’s MELD or PELD score increases over time, only the waiting time
at the higher level will count. (For example, if you have waited 40 days with
a score of 12, and 5 days with a score of 15, you would only get credit for 5
days of waiting time at the score of 15.) However, if the patient’s MELD or
PELD score decreases again, he or she would keep the waiting time gained
at the higher score. (Using the earlier example, if your score goes from 12
to 15 and back to 12, you would have 45 days of waiting time at the score of
12.) Patients initially listed as a Status 1 also keep their waiting time if their
condition improves and they later receive a MELD/PELD score.
Patients with higher MELD/PELD scores will always be considered before
those with lower scores, even if some patients with lower scores have waited
longer. (For example, a patient waiting for one day with a score of 30 will
come ahead of a patient with a score of 29, even if the patient with a 29 has
waited longer. This is because the patient with a score of 30 has a higher
risk of dying without a transplant.)
What if I had been on the waiting list when the system changed?
For the first year of the MELD and PELD system, a transition plan was in place
for liver candidates awaiting a transplant at the time of the change to maintain
their priority gained under the previous policy. After the transition period
ended, those candidates still awaiting a transplant were prioritized only by
their MELD or PELD score.
If you were listed for transplant at the time the policy became effective
(February 27, 2002), your transplant team would best be able to address any
questions about the transition and/or your current medical status.
All patients newly listed for a liver transplant since February 2002 receive
priority only by their MELD or PELD score, based on their current lab results.
Do MELD and PELD account for all conditions?
MELD/PELD scores reflect the medical need of most liver transplant candidates.
However, there may be special exceptions for patients with medical conditions
not covered by MELD and PELD. If your transplant team believes your case
qualifies for an exception, they may submit information to a review board
and request a higher score. The review board will consider the medical facts
and determine whether or not to grant a higher score.
Is this system likely to change?
Liver allocation policy based on MELD and PELD has already been changed
as transplant professionals have applied and learned from the system, and
future changes will likely be required to better meet patients’ needs. In fact,
this system is designed to be flexible and allow improvements. In transplantation,
as in all scientific fields, new studies are taking place all the time to learn how
to save more lives and help people live longer and better.
MELD/PELD Calculator Documentation
The MELD/PELD Calculator is a utility that allows you to enter hypothetical or actual parameters and calculate a MELD or PELD score for an individual patient.
The MELD/PELD Calculator provided on this site 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 patients who have had dialysis twice within the last week, the creatinine value will be automatically set to 4 mg/dl.
The MELD Calculator is used for patients who are 12 years and older. After entering
the laboratory values,you may calculate the score by clicking Calculate. The MELD score displays in the MELD Score field.You can also calculate a score by simply tabbing into the MELD Score field.
The PELD score calculation uses:
Albumin (g/dl)
Bilirubin (mg/dl)
INR
Growth failure (based on gender, height and weight)
Age at listing
The PELD Calculator is used for patients who are under 12 years old. After entering the laboratory values,you may calculate the score by clicking Calculate. The PELD score displays in the PELD Lab Value field. You can also calculate a score by simply tabbing into the PELD Lab Value field.
MELD Formula
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)
+ 0.643?
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.
The maximum serum creatinine considered within the MELD score equation is 4.0 mg/dl (e.g. if you enter
4.3 for serum creatinine the formula will calculate 0.957 x Loge(4.0) for the serum creatinine portion of the
MELD formula).
If you answer Yes to the question: “Had dialysis twice within a week prior to Serum Creatinine test?” then
the MELD score will be calculated with a serum creatinine value of 4.0 mg/dl. For example, if you enter
3.0 for serum creatinine and answer Yes to the dialysis question, then the formula will calculate 0.957 x
Loge(4.0) for the serum creatinine portion of the MELD formula.
PELD Formula
The PELD score is calculated using the following formula:
PELD Score = 0.480 x Loge(bilirubin mg/dL)
+ 1.857 x Loge(INR)
- 0.687 x Loge(albumin g/dL)
+ 0.436 if patient is less than 1 year old (scores for patients listed for liver transplantation
before the patient's first birthday continue to include the value assigned for age (< 1
Year) until the patient reaches the age of 24 months)
+ 0.667 if the patient has growth failure (<-2 Standard deviation)
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 PELD score calculation