The United Network For Organ Sharing uses measurements of clinical and laboratory problems to divide patients into groups that determine who is in most critical need of a liver transplant. In early 2002, UNOS enacted a major modification to the way in which people were assigned the need for a liver transplant. Previously, patients awaiting livers were ranked as status 1, 2A, 2B and 3, according to the severity of their current disease. Although the status 1 listing has remained, all other patients are now classified using the Model for End-Stage Liver Disease (MELD) scoring system if they are aged 18 years or older, or the Pediatric End-Stage Liver Disease (PELD) scoring system if they are younger than 18 years. These scoring methods were set up so that donor livers could be distributed to those who need them most urgently.
Status 1 (acute severe disease) is defined as a patient with only recent development of liver disease who is in the intensive care unit of the hospital with a life expectancy without a liver transplant of fewer than 7 days.
MELD scoring is a system is based on the risk or probability of death within 3 months if the patient does not receive a transplant. The MELD score is calculated based only on laboratory data in order to be as objective as possible. The laboratory values used are a patient's creatinine, bilirubi, and International Normalized Ratio (INR). Certain medical conditions also influence MELD scores. _A patient's score can range from 6 to 40. See the "Model for End-stage Liver Disease" section for more information on MELD.
PELD scoring is a special scoring formula in place for pediatric patients under the age of twelve. This system is also based on the risk or probability of death within 3 months if the patient does not receive a transplant. The PELD score is calculated based on laboratory data, age and growth parameters. The laboratory values used are a patient's albumin, bilirubin and INR . These values are used together with the patient's age and degree of growth failure to determine a score that can range from 6 to 40. See the "PELD Model" section for more discussion of PELD scoring.
Status 7 (inactive) is defined as patients who are considered to be temporarily unsuitable for transplantation.
Based on the MELD/PELD system, livers are first offered locally to status 1 patients, then according to patients with the highest MELD or PELD scores. Next, if there are no local recipients, the liver is offered regionally, in the same order, and finally, on a national level. In the event of a liver becoming available to 2 patients with the same MELD score and blood type, time on the waiting list becomes the deciding factor.