*Purpose: Patients with end-stage liver disease (ESLD) who undergo liver transplantation experience significant survival benefit, with a 1-year survival rate after liver transplantation of 91%. After early landmark studies, more recent data have failed to correlate transplant volume with outcomes in adults; however, the field lacks standardized volume thresholds. The aim of the present study is to use a data-centered method to identify volume thresholds predicting distinct outcomes for liver transplant centers.

*Methods: All liver transplants performed on patients over the age of 18 between 2003 and 2017 in the United Network for Organ Sharing (UNOS) database were reviewed. Patients listed for or receiving other organs and transplants performed in centers that were active for less than three of the ten years of the volume calculation period (2005-2015) were excluded. A small number (under 1%) of patients were excluded due to lack of follow-up data. Stratum-specific likelihood ratios (SSLR) were calculated to establish volume thresholds predictive of the primary outcome of 1-year mortality. Demographic and outcomes data were compared between volume strata and significance tested using chi-squared tests or analysis of variance (ANOVA).

*Results: A total of 89,198 recipients was included in the final cohort. We identified two thresholds based on SSLR analysis at 72 and 104 liver transplants per year, which yielded three distinct volume strata: low- (under 72), mid- (72-104), and high-volume (over 104). The mid-volume centers have the shortest lengths of stay (14.7 days, vs 16.8 and 17.4 for low- and high-volume) and highest 1-year patient survival (90.2% for mid- vs 89.6 and 89.5% for low- and high-volume), as well as highest 30-day survival. The apparent lack of mortality advantage of high-volume centers likely relates to their older and more seriously ill recipients, more of whom present from intensive care (14% vs 9.5% for mid-volume), and higher utilization of extended-criteria donors (25.4% vs 24.3% and 22.2% for low- and mid-volume). High-volume centers attain shorter wait times (236 days vs 272 and 246 respectively) and lower rates of rejection in the first year (6.6%, vs 8.5 and 10.3% respectively).

*Conclusions: Our study highlights that a larger volume of liver transplants does not necessarily translate to better outcomes. While a data-driven approach with SSLRs does identify three distinct volume levels, no one level is superior across all measures. Our study adds to the existing literature by demonstrating specific differentiating features and highlighting outcomes measures that each volume level most needs to address.

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