MELD Exceptions and Rates of Waiting List Outcomes

Abstract

Model for End-stage Liver Disease (MELD)-based allocation of deceased donor livers allows exceptions for patients whose score may not reflect their true mortality risk. We hypothesized that organ procurement organizations (OPOs) may differ in exception practices, use of exceptions may be increasing over time, and exception patients may be advantaged relative to other patients. We analyzed longitudinal MELD score, exception and outcome in 88 981 adult liver candidates as reported to the United Network for Organ Sharing from 2002 to 2010. Proportion of patients receiving an HCC exception was 0-21.4% at the OPO-level and 11.9-18.8% at the region level; proportion receiving an exception for other conditions was 0.0%-13.1% (OPO-level) and 3.7-9.5 (region-level). Hepatocellular carcinoma (HCC) exceptions rose over time (10.5% in 2002 vs. 15.5% in 2008, HR = 1.09 per year, p<0.001) as did other exceptions (7.0% in 2002 vs. 13.5% in 2008, HR = 1.11, p<0.001). In the most recent era of HCC point assignment (since April 2005), both HCC and other exceptions were associated with decreased risk of waitlist mortality compared to nonexception patients with equivalent listing priority (multinomial logistic regression odds ratio [OR] = 0.47 for HCC, OR = 0.43 for other, p<0.001) and increased odds of transplant (OR = 1.65 for HCC, OR = 1.33 for other, p<0.001). Policy advantages patients with MELD exceptions; differing rates of exceptions by OPO may create, or reflect, geographic inequity.

Figure 1. Construction of the study population

Figure 2. Distribution of MELD scores, and 90-day outcomes by MELD score

Left panel shows the distribution of person-days at each MELD score for non-exception person-time, HCC exception person-time, and other exception person-time. Right panel shows risk of various outcomes (MELD decrease, no change, MELD increase, transplantation, death) by MELD score for candidates without MELD determined by lab values (calculated meld/cMELD) and with by exception score (exception meld/eMELD), separately for HCC and other exceptions. Gray, orange, green, purple, and blue represent the risk of decrease, no change, increase, transplantation, and death respectively.

Figure 3. Survival of HCC exception patients after removal from the liver waiting list due to deteriorating health

62% of HCC patients who dropped out due to deteriorating health died within one year.

Figure 4. Cumulative incidence of HCC and other exceptions, stratified by year of waiting list registration

Patients added to the waiting list in later years had a higher chance of being granted an exception, both for HCC and other exceptions.

Figure 5. 90-day rates of transplantation and death while waiting, by initial allocation aMELD score, across OPOs (5A, 5B) and regions (5C, 5D)

Each box plot represents two aMELD points (e.g. the left most box represents aMELD scores of 6 or 7), except for the right most box which represents patients with an aMELD of exactly 40.

Figure 6. Proportion of patients who received HCC and other exceptions, by OPO (6A) and region (6B)

HCC exceptions are more common than other exceptions. The proportion of HCC exception shows no apparent relation to the proportion of other exceptions at the OPO level (correlation coefficient = 0.14), but is inversely related to the proportion of other exceptions at the regional level (correlation coefficient=−0.67).