Integrative Muscle-Adipose Score (IMAS): A Novel Unified, Sex-Sensitive Body Composition-Based Survival Predictor Enhancing Risk Stratification After Liver Transplantation.

OBJECTIVE: To investigate the potential of integrating muscle and fat compartments into a novel and unified score for outcome prediction in a bicentric European cohort of LT recipients. BACKGROUND: Body composition (BC) reflects nutritional status and metabolic reserves and influences outcomes after orthotopic liver transplantation (LT). Validated tools for predicting long-term survival after LT remain scarce. Increasing evidence highlights sex-specific disparities in post-transplant outcomes. STUDY DESIGN: A total of 695 adult patients undergoing LT at Charité-Berlin (n=412, 2010 to 2020; discovery cohort) and University Hospital Aachen (n=283, 2010 to 2018; validation cohort) were included. CT-based BC was assessed at lumbar level 3/4. Muscle mass, quality, and adipose tissue were integrated into the integrative muscle-adipose score (IMAS) and correlated with survival and postoperative morbidity. RESULTS: Median follow-up was 54 (discovery) and 47 months (validation). A total of 31% of recipients were female. IMAS quartiles significantly stratified overall survival in both cohorts (P<0.01). Low IMAS was independently prognostic of overall survival in both cohorts. Sex-specific IMAS cutoffs were independently prognostic in both sexes (♂︎: HR=1.89, 95% CI: 1.37-2.70, P=0.001; ♀︎: HR=2.04, 95% CI: 1.17-3.55, P=0.012), whereas the BAR score failed to predict long-term survival in female recipients. Across sexes, low IMAS was associated with significantly lower restricted mean survival time at 5 years (♂︎ 43.2 vs. 50.16 mo, P<0.001; ♀︎ 44.2 vs. 51.71 mo, P=0.013) and a higher Comprehensive Complication Index 90 days after LT. CONCLUSION: The IMAS provides a novel, reproducible sex-sensitive framework for long-term outcome prediction after LT.