Waitlist Calculation Documentation


The liver waiting list calculator was developed to help liver transplant candidates and their doctors understand what may occur in the coming year. The tool uses historical data to show what happened to patients on the liver transplant waiting list for 30, 60, 90, 180, or 365 days. Possible outcomes include:

  • Receiving a liver from a deceased donor
  • Receiving part of a liver from a living donor
  • Dying or being removed from the waiting list due to becoming too sick to undergo transplant
  • Being removed from the waiting list because of improved condition or for other reasons (undergoing transplant at another program, transferring to another program, undergoing transplant in another country, no longer being reachable by the program)
  • Remaining on the waiting list

In the United States, livers are generally allocated based on the medical urgency of the candidate (using the model for end-stage liver disease [MELD] score) and the distance the donor organ would need to travel. For more information on the allocation process, learn how UNOS matches organs.

The tool provides information at the following geographic levels:

  • Transplant center: First, the tool shows what happened to transplant candidates listed at a selected transplant center
  • Donation service area (DSA): Each US DSA is served by an organ procurement organization (OPO) responsible for recovering deceased donor organs
  • Organ Procurement and Transplantation Network (OPTN) region: Find more information about the 11 US OPTN regions
  • National: All US liver transplant candidates are combined

The tool provides data for the four geographic regions so users can compare what occurs within centers, DSAs, OPTN regions, and the nation as a whole. If any specific grouping includes fewer than five candidates, the data are not shown. In these cases, combining data at the DSA, OPTN region, or national level may result in sufficient group sizes to include them in results.

The tool is built to display outcomes from any day on the waiting list, not only from the candidate's first day. A candidate's priority on the list is determined by the MELD score. MELD is calculated using serum creatinine, bilirubin, and international normalized ratio (INR) values and by whether the candidate received kidney dialysis in the last week. These factors result in a measured, or laboratory, MELD score. Also, some candidates are awarded exception MELD scores owing to other underlying conditions that warrant more prioritization (eg, certain types of liver cancer). The tool allows the user to narrow results by whether the candidate has an exception MELD score. Please consult with your care team for more information on exception MELD scores.

The tool uses historical data to derive the results. A snapshot of the liver transplant waiting list was taken on in a two-year period about 30 days apart. Candidates were followed for 30, 60, 90, 180, or 365 days to observe outcomes. To create non-overlapping observation windows for the different outcomes studied, only certain days are included in the calculations for the different timeframes, as indicated in the following table:


Date Sampled 30 days  60 days  90 days  180 days  365 days
8/19/2019 X X X X X
9/19/2019 X        
10/20/2019 X X      
11/20/2019 X   X    
12/21/2019 X X      
1/21/2020 X        
2/21/2020 X X X X  
3/23/2020 X        
4/23/2020 X X      
5/24/2020 X   X    
6/24/2020 X X      
7/25/2020 X        
8/25/2020 X X X X X
09/25/2020 X        
10/26/2020 X X      
11/26/2020 X   X    
12/27/2020 X X      
1/27/2021 X        
2/27/2021 X X X X  
3/30/2021 X        
4/30/2021 X X      
5/31/2021 X   X    
7/1/2021 X X      
8/1/2021 X        


Candidates who were adults (18 years or older) at listing were included in the analysis. Candidates who were Status 1A, the most critically ill, were excluded. Candidates listed at multiple programs were included separately, as if they were two different candidates; however, a transplant event was counted only toward the program in which the transplant took place. Thus, for a candidate listed at a program in New York and a program in Washington, DC, who underwent transplant at the Washington, DC, program, the tool counts the transplant event toward the Washington, DC, program. Candidates listed for more than one organ (eg, kidney and liver) were included in the analysis. Liver-intestine candidates with higher priority were included as having exception MELD scores that reflect that priority. Results are presented as counts and percentages of all candidates meeting the selection criteria (blood type [optional], age group [optional], MELD score range, and exception MELD score status [optional]).

The tool is intended solely for informational purposes and is not meant to offer advice to candidates or their doctors on the appropriate treatment for a specific candidate. Patients should always discuss their treatment options with their care providers.