(1310) Glomerular Filtration Rate Using Serum Creatinine or Cystatin C in the Pediatric Intensive Care Unit

Introduction: Acute kidney injury (AKI) is a frequent occurrence in the Pediatric Intensive Care Unit (PICU) and is associated with increased morbidity and mortality. Both serum creatinine (Scr) and cystatin C (CysC) can be used to calculate the glomerular filtration rate (GFR). Data comparing these two markers to calculate GFR, and subsequently identify AKI, in the PICU are lacking.

Methods: We conducted a retrospective single center study of patients aged 1-25 years old, who were admitted to the PICU and had a Scr and CysC obtained on the same day. Patients were excluded if they also received renal replacement therapy. The GFR in patients 1- < 18 years was calculated using the Bedside Schwartz and Cystatin C-based equation (2012), and for patients 18- < 25 the CKD-EPI creatinine equation (2021) and CKD-EPI cystatin C equation (2012). All patients also had GFR calculated using the CKiD U25 Scr and CKiD U25 CysC equations. Comparisons were made using Student’s T-test or Pearson’s chi square as appropriate.

Results: A total of 142 patients (119 pediatric), totaling 279 laboratory evaluations (223 pediatric) met criteria. In the pediatric group, there were no differences between Bedside Schwartz and CKiD U25 Scr (p=0.6) and Cystatin-C 2012 and CKiD U25 CystC (p=0.89), but there were differences between any equation using Scr or CysC (p < 0.01). CysC equations identified 88 instances with GFR < 60 ml/min/1.73m2, whereas Scr equations identified only 11 instances (p < 0.01). The adult cohort had a difference between CKD-EPI creatinine (2021) and CKiD U25 Scr (p < 0.01) and no difference between CKD-EPI cystatin C (2012), and CKiD U25 CysC (p=0.54). There were differences between any equation using Scr or CysC (p < 0.01). CystC equations identified 35 instances with GFR < 60 ml/min/1.73m2, whereas Scr equations identified only 11 instances (p < 0.01).

Conclusions: Equations using Scr and CysC result in different GFR values and identify AKI at different rates. CysC may be more accurate at identifying AKI.