Factors Associated With Waiting Time on the Liver Transplant List: An Analysis of the United Network for Organ Sharing (UNOS) Database

Abstract

Introduction: Liver transplantation (LT) is an important treatment for acute liver failure and end-stage liver disease. The increasing demand on limited resource results in increased wait time on the LT list. More than 2000 candidates die each year waiting for a liver transplant. In 2002, the Model for End-stage Liver Disease (MELD) score was incorporated to prioritize patients awaiting LT. Although there is data on MELD score affecting wait times on the LT list, there continues to be paucity of literature about other factors that could affect the wait time. We aimed to evaluate the factors affecting LT waiting times in the United States. Methods: Using the UNOS database, patients aged 12 to 75 years listed for LT between the years of 2002 to 2015 were included. We excluded patients prior to implementation of MELD score in 2002. A generalized linear model to predict wait time in days after performing logistic transformation was used. Variables tested in the model included patient characteristics (age at listing, body mass index, presence of ascites, hepatoceullar carcinoma and need for mechanical ventilation), laboratory values (serum bilirubin, albumin, sodium, creatinine, international normalized ratio) as well as other factors (ABO blood type, region of listing, primary payer, ethnicity and listing for simultaneous transplantation). We used backward elimination to maintain significant predictors in our model. Results: A total of 75,771 patients were included in the final analysis. Factors that were associated with wait times on the LT list are summarized in Table 1. The components of the MELD score, i.e. serum bilirubin, INR and creatinine were associated with shorter wait times. Other factors associated with shorter wait times were the need of mechanical ventilation and region of transplantation (region 3). ABO blood type, primary payer and placement of transjugular porto-systemic shunt (TIPS) also influenced time on the LT wait list.Table: Factors affecting wait times on the liver transplantation list.Conclusion: As expected, the MELD score was important in predicting the wait time on the LT list. However, other factors also strongly influenced the wait times. ABO blood type, region of transplantation, primary payer type and placement of TIPS also influenced wait times on the LT list significantly. Further research is needed to address reasons for the variation in wait times between regions and payment systems in an attempt to decrease wait times, standardize the listing process and improve patient outcomes.