Core outcome sets and benchmarking complications: Defining best practices for standardized outcome reporting in liver transplantation.

The comparison of outcomes in liver transplantation (LT) is hampered by using clinically non-relevant surrogate endpoints and considerable variability in reported relevant post-transplant outcomes. Such variability stems from non-standard outcome measures across studies, variable definitions of the same complication, and different timing of reporting. The Clavien-Dindo classification was established to improve the rigor of outcome reporting but is non-specific to an intervention and there are unsolved dilemmas specifically related to liver transplantation. Core Outcome Sets (COS) have been used in other specialties to standardize outcomes research, but have not been defined for LT. Thus, we use the five major benchmarking studies published to date to define a 10-measure COS for LT using previously validated metrics. We further provide standard definitions for each of the 10 measures that may be used in international research on the topic. These definitions also include standard time-points for recording to facilitate between-study comparisons and future meta-analysis. These 10 outcomes are paired with 3 validated, procedure-independent metrics, including the Clavien-Dindo Classification and the Comprehensive Complications Index (CCI®). The Clavien scale and CCI® are specifically reviewed to enhance their utility in LT, and their use along with the COS is explored. We encourage future studies to employ this COS along with the Clavien-Dindo grading system & CCI® to improve reproducibility and generalizability of research concerning liver transplantation.