Machine Perfusion or Straight to Transplant? Predictive Value of Flavin Mononucleotide Levels in Flush Solution of Human Liver Allograft.

OBJECTIVE This study examined the predictive value of Flavin Mononucleotide (FMN) levels in the flush solution used during cold storage of donor livers on outcomes post-transplantation. BACKGROUND Static cold storage for liver grafts induces hypoxia with subsequent impaired mitochondrial function and Flavin Mononucleotide (FMN) release upon reperfusion. METHODS This study enrolled 62 recipients who received whole liver grafts from donation after brain death (n=50) and circulatory death donors (n=12) between June 2022 and July 2023. FMN concentrations were measured in flush solutions on the back-table. ROC-curve analysis identified an FMN level cut-off for graft survival. Post-transplant outcomes were examined according to FMN levels. RESULTS FMN level was significantly associated with graft survival, with an area-under-the-curve (AUC) of 0.858 (95%CI: 0.754-0.963, P<0.001), outperforming the donor risk index (AUC 0.571, 95%CI: 0.227-0.915, P=0.686). The study cohort was divided into low-FMN (<37.5 ng/mL, n=40) and high-FMN groups (≥37.5 ng/mL, n=22). The low-FMN group had superior one-year graft survival compared with the high-FMN group (100% vs. 77%, P=0.003). Levels of transaminases within 7 days post-transplant were significantly higher in the high-FMN group (P=0.003). The high-FMN group developed acute rejections (41% vs. 15%, P=0.023) and early allograft dysfunction (50% vs. 20%, P=0.014) more frequently. Median comprehensive complication index in the high-FMN group was significantly higher (54 [interquartile range, 40-78] vs. 42 [interquartile range, 28-52], P=0.017). CONCLUSION The FMN level measured in donor livers' cold storage flush solution is a valid biomarker to predict post-transplant outcomes. Liver grafts with high FMN levels may benefit from machine perfusion to improve outcomes.