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In the United States the United Network for Organ Sharing (UNOS) is the national organization that sets policy and enforces the rules for organ allocation. UNOS rules determine who receives a liver and when. All transplant centers must abide by UNOS rules to remain certified to perform transplants.  UNOS divides the country into 11 distinct organ sharing regions as shown on this map.


For liver candidates, UNOS has developed a scoring system called MELD (Model End-Stage Liver Disease), to determine the need for a liver. The scoring system is based upon blood tests for bilirubin, creatinine, and INR (International Normalized Ratio, also called prothrombin time). Scores range from 6 (low level of illness) to 40 (gravely ill). For persons under age 12 the calculator is called PELD (Pediatric End-Stage Liver Disease).

A recent UNOS statement indicates, “Of candidates listed in the United States with an initial MELD or PELD score between 19 and 24, half receive a liver transplant within approximately 15 weeks of being listed. Of those listed with an initial MELD or PELD score of 25 or higher, half receive a transplant within 20 days of listing. Candidates with lower MELD/PELD priority may often wait months to years for a transplant opportunity.”

The statement above refers to the average wait time nationally. The specific center you are considering may not fit this profile.

Until 2002, time spent on the waiting list was the determining factor in who received a liver. The more time you spent on the list meant you rose up the list and were likely to get a liver transplant once you’d accrued the most time waiting.

However, today the MELD and PELD scores tell surgeons who is sickest and requires a liver first. For some liver conditions a special exception can be made to raise the MELD or PELD score. If your doctor thinks you present special circumstances that are unaddressed by the MELD/PELD system, the transplant center can ask a UNOS Regional Review Board for an exception. Exceptions are given rarely, however. The hepatologist you are working with can explain the scoring system and where you fit in it. The MELD/PELD system has reduced the number of deaths of people on the waiting list by offering livers for the sickest patients. Researchers have found that transplantation too early, at a low MELD score, has resulted in increased mortality.

MELD/PELD Calculators

The UNOS website has a calculation feature page in which you can calculate the MELD and PELD score if you know the values of certain recent blood tests.

MELD Calculator

PELD Calculator

As you get closer to your transplant you will be required to update blood tests on a specific, required schedule. If you do not keep the tests updated, informing your transplant center, you can be given a much lower MELD or PELD score until you get lab tests done. Your center’s transplant coordinator will assist you in understanding the schedule for blood tests and how to have the results sent to the center.