Discordance in categorization of acute-on-chronic liver failure in the United Network for Organ Sharing database

Abstract

Background & aims: Studies regarding acute-on-chronic liver failure (ACLF) among liver transplant (LT) candidates from the United Network for Organ Sharing (UNOS) database are being used to inform LT policy changes worldwide. We assessed the validity of identifying ACLF in UNOS.

Methods: We performed stratified random sampling among 3 US LT centers between 2013-2019 to obtain a representative patient sample across ACLF grades. We compared the concordance of ACLF classification by UNOS vs. blinded manual chart review, according to EASL-CLIF.

Results: Among 481 sampled LT registrants, 250 (52%) had no ACLF, 75 (16%) had ACLF grade 1, 79 (16%) had ACLF grade 2, and 77 (16%) had ACLF grade 3 per UNOS categorization. Concordance of ACLF grade by UNOS vs. chart review was: 72%, 64%, 56%, and 64% for no ACLF, grade 1, grade 2, and grade 3, respectively, with an overall Cohen's kappa coefficient of 0.48 (95% CI 0.42-0.54). Absence of acute decompensation was the most common reason for overestimation, and discordant brain and respiratory failure categorization were the most common reasons for underestimation of ACLF by UNOS.

Conclusions: In this retrospective multi-center study, ACLF categorization by UNOS showed weak agreement with manual chart review. These findings are informative for ongoing allocation policy discussions, highlight the importance of prospective studies regarding ACLF in LT, and should encourage UNOS reform.

Lay summary: Acute-on-chronic-liver-failure (ACLF) is a specific and common form of liver failure associated with high death rates. Studies have been published using the United States transplant registry (UNOS) to identify and describe outcomes of transplant candidates and recipients with ACLF, and these data are driving policy changes for transplant allocation around the world, but nobody has shown whether these data are reliable. We found that UNOS was not categorizing ACLF in concordance or accurately when compared to chart review, which shows the need for UNOS reform and non-UNOS studies to appropriately inform policies regarding the transplantation of patients with ACLF.

Keywords: ACLF; UNOS; bias; concordance; misclassification.