Determination of the Discordance Rate Between the CKD-EPI eGFRcr-cys Equation and Measured 8-Hour Urinary Creatinine Clearance

Background: Chronic Kidney Disease Epidemiology (CKD-EPI) estimated glomerular filtration rate (eGFR) equations are recommended over Cockcroft-Gault creatinine clearance, but preference compared to measured urinary creatinine clearance (mCrCL) is less certain. Both eGFR and mCrCL have unique advantages and limitations. Serum creatinine (SCr) and cystatin C (cysC) based eGFR (eGFRcr-cys) and 8-hour measured urinary creatinine clearance (mCrCL 8 ) have yet to be compared in acutely ill patients. Objective: The primary objective of this study was to determine the discordance rate between eGFRcr-cys and mCrCL 8 estimations of kidney function in hospitalized patients. Discordance rate was defined as the overall percentage of patients in which there was a 30% or greater difference between eGFRcr-cys and mCrCL 8 . Methods: This was a single-center, retrospective, observational cohort study of adults admitted between 1/1/2023 and 8/31/2025 with SCr and cysC ordered within 72-hours of mCrCL 8 . Data was collected via chart review; eGFRcr-cys was adjusted for individual patient body surface area to mL/min for mCrCL 8 comparison. Demographic data was analyzed via descriptive statistics. Statistical analysis was performed by Fisher’s exact test for nominal data, T -test for normally distributed data and Mann-Whitney U test for non-normally distributed data. Results: The study included 74 patients (95.9% critically ill, 47.3% female; median age 50 [34.5-67.5] years) with a median SCr 0.60 [0.43-1.05] mg/dL and cysC 1.29 [0.96-2.31] mg/L. Median eGFRcr-cys was 75.1 [49.3-117.4] mL/min and mCrCL 8 was 94.8 [43.6-160.9] mL/min. The discordance rate was 59.5%. Discordance was oftentimes resultant from mCrCL 8 being higher than eGFRcr-cys (63.6% of the discordant cases). Conclusion: The eGFRcr-cys was discordant with mCrCL 8 in 59.5% of predominately ICU patients. Discordance was usually a result of mCrCL 8 estimating higher than eGFRcr-cys. Additional studies are needed to definitively discern clinical scenarios where 1 type of kidney function estimation approach is preferred over another.