492 - Discordance of creatinine and cystatin C-based estimated glomerular filtration rate measurements in pediatric intestinal transplant patients

Publication Number: 2478.492

Elizabeth Rivas, University of Miami Leonard M. Miller School of Medicine, Miami Lakes, FL, United States; Tara Gavcovich, University of Miami Leonard M. Miller School of Medicine, Miami, FL, United States; Marissa Janel Defreitas, University of Miami Leonard M. Miller School of Medicine, Miami, FL, United States; Wacharee Seeherunvong, University of Miami Leonard M. Miller School of Medicine, Miami, FL, United States; Carolyn Abitbol, University of Miami Leonard M. Miller School of Medicine, Miami, FL, United States; Jayanthi Chandar, University of Miami and Miami Transplant Institute, Miami, FL, United States; Garcia Jennifer, University of Miami, Miami, FL, United States; Chryso Katsoufis, University of Miami Leonard M. Miller School of Medicine, Miami, FL, United States

Background: Pediatric recipients of intestinal transplants are at increased risk of kidney dysfunction, yet the estimation of their function is understudied. Serum creatinine (SCr) based estimated glomerular filtration rate (eGFR) is the most utilized, but may overestimate renal function due to its reliance on muscle mass given the increased risk of malnutrition in intestinal failure patients. Serum cystatin-C (CysC) eGFR, independent of muscle mass, may be more accurate.

Objective: This study aimed to compare eGFR measurements based on SCr and CysC CKiD U25 formulas in pediatric intestinal transplant recipients.

Design/Methods: Pediatric intestinal or multivisceral (MVT) transplant recipients, excluding those with a kidney allograft, from 2013-2023 were included. Paired SCr and CysC measurements were collected for eGFR calculation. Absolute eGFR difference (eGFRdiff) was calculated by subtracting SCr eGFR from CysC eGFR, and values were compared in both pre-transplant and post-transplant samples using linear regression, Bland Altman plots, and paired t-test and Wilcoxon tests.

Results: 57 patients were included (58% male), with a median age at transplant of 4 years (IQR 2.5, 9). Transplant types included: MVT (74%), isolated intestinal (25%), and modified MVT (2%). Short bowel syndrome (67%) and dysmotility (28%) were the most common indications for transplant. A total of 125 pre-transplant eGFRs were calculated, and 70% of pairs had a CysC eGFR less than SCr eGFR. Median eGFRdiff was -18.2mL/min/1.73m2 with 50% of pairs differing by more than 30mL/min/1.73m2 (Figure 1a). 609 post-transplant eGFRs were calculated with 76% of pairs with CysC eGFR less than SCr eGFR. Median eGFRdiff was -19.6mL/min/1.73m2, and 44% of pairs differed in eGFR calculation by more than 30mL/min/1.73m2 (Figure 1b). Bland Altman plot revealed a bias of -24.5 and 95% limit of agreement -101.5 to 52.5 (Figure 2), and there were significant differences between SCr eGFR, CysC eGFR and combined eGFR (p < 0.001) in both the pre- and post-transplant cohorts (Figure 3).

Conclusion(s): In pediatric intestinal transplant recipients, eGFR differed significantly depending on the method used, with a high discordance between serum marker eGFRs both in the pre- and post-transplant setting. We conclude that CysC eGFR is important for routine surveillance in this population, as SCr may be over-estimating kidney function in the setting of malnutrition. Improved GFR estimates, are critical in assessing clinical course and medication dosing.

Figure 1
a. Pre-transplant serum Cr-based eGFR vs absolute eGFRdiff, R2 = 0.44, p < 0.001. b. Post-transplant serum Cr-based eGFR vs absolute eGFRdiff, R2 = 0.50, p < 0.001.

Figure 2
Bland Altman Plot of post-transplant CKiD U25 eGFR, SCr vs CysC. Bias -24.5, standard deviation 39.3, 95% limit of agreement -101.5 to 52.5.

Figure 3
Comparison of eGFRs in both pre-transplant (a.) and post-transplant (b.) sampling, *p < 0.001.