In order to undergo a liver transplant, a patient must be placed on the national waiting list. The list is managed by the United Network for Organ Sharing (UNOS), which collects and manages all data that pertain to the patient waiting list, organ donation and matching, and transplantation occurring on the OPTN, the nation's organ transplant network. All liver transplant candidates in the United States must be listed with UNOS before a donor liver can be allocated.
Currently there are nearly 17,000 people waiting for a liver transplant in the United States. The median national waiting time in 2006 was 321 days.* This does not take into consideration in what part of the country a patient lives or their status at the time of transplant. Therefore, a patient's median wait may be longer or shorter depending on how sick the patent is or where they live.
The severity of liver disease in patients waiting for transplant ranges from having mild complications to being critically ill in the intensive care unit. UNOS has developed a scoring system known as the Model for End-Stage Liver Disease, or MELD, in which the sickest patients are given priority for organ allocation. Every center in the U.S. must follow the UNOS MELD system.
The MELD system involves 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:
- Bilirubin, which measures how effectively the liver excretes bile;
- INR (prothrombin time), which measures the liver's ability to make blood clotting factors; and
- 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. Candidates age 11 and younger are placed in categories according to the Pediatric End-stage Liver Disease (PELD) scoring system. A MELD/PELD brochure and calculator are available on the UNOS website.