793: Cystatin C and Creatinine-Based Egfr Discordance in Liver Transplant Patients With Renal Recovery

Introduction: Renal dysfunction in liver transplant (LT) candidates has been associated with decreased post-transplant survival with duration of pre-transplant renal replacement therapy (RRT) highly predictive of spontaneous renal recovery (RR) post-transplant. Studies have shown that cystatin C (CysC) may be a more accurate predictor of renal function than serum creatinine (SCr) which could potentially impact medication dosing. The objective of this study was to evaluate the discordance rate (DR) between estimated glomerular filtration rate (eGFR) CysC and SCr in post-LT patients with RR. Methods: This was a single-center, retrospective study of adult post-LT patients with RR from May 2020-2025. Patients with post-LT eGFRCysC and eGFRCr measured within 24 hours of each other were included. Patients were excluded if they received RRT within 72 hours of CysC measurement, had a life expectancy < 48 hours post-LT, or received a simultaneous liver-kidney transplant. The primary outcome was the DR between eGFRCr and eGFRCysC. The secondary outcome was the total number of renally eliminated medications affected by this discordance. Results: Of the 1147 LTs evaluated, 60 patients (50% male; mean age 55.1 years [13.6]; mean SCr 1.3 mg/dL [0.7]; mean CysC 2.6 mg/L [0.8]) met inclusion criteria. The mean eGFRCr was 66.6 mL/min [30.5] and eGFRCysC was 24.6 mL/min [11.1]. The mean difference in eGFRCr-eGFRCysC was 42.0 mL/min [23.4], p-value < 0.05, with an absolute difference of ≥ 30% and ≥ 15 mL/min, in 98% and 88% of the cases, respectively. At the time of biomarker assessment, 175 renally adjusted medications were identified with an average of 3 medications [2-4]/patient (antibiotics: 26.9%, antivirals: 28.0%, anticonvulsants: 5.1%, and antifungals: 3.4%). Conclusions: Significant discordance was demonstrated between SCr and CysC-based estimates of kidney function, thereby impacting dosing of medications in post-LT patients. Further research should identify the optimal method for estimating kidney function to ensure safe and effective medication dosing.