Hyperfiltration affects accuracy of creatinine eGFR measurement

Area of Science:

• Pediatric Nephrology
• Renal Physiology
• Biomarker Analysis

Background:

• Estimating glomerular filtration rate (eGFR) is crucial for diagnosing and managing kidney disease.
• Commonly used markers include creatinine, cystatin C (CysC), and beta trace protein (BTP).
• The accuracy of eGFR may be influenced by physiological states like hyperfiltration and variations in filtration fraction (FF).

Purpose of the Study:

• To investigate the impact of hyperfiltration and filtration fraction (FF) on the accuracy of different eGFR formulas in pediatric patients.
• To determine if creatinine-based eGFR is affected by effective renal plasma flow (ERPF) and FF, unlike CysC and BTP.

Main Methods:

• Simultaneous measurements of GFR and ERPF were performed in 127 pediatric patients with renal diseases.
• GFR was measured using 51Cr-EDTA renal scan, and ERPF was determined by 131I-hippurate clearance.
• eGFR was calculated using Schwartz (creatinine), Filler (CysC), and Benlamri (BTP) formulas, with FF calculated as GFR/ERPF.

Main Results:

• A significant negative correlation was observed between the error in Schwartz eGFR (eGFR-GFR) and FF.
• No significant correlation was found between FF and the error for CysC and BTP eGFRs.
• This suggests that CysC and BTP are less susceptible to variations in FF compared to creatinine.

Conclusions:

• The accuracy of creatinine-based eGFR (Schwartz formula) is significantly affected by filtration fraction in pediatric patients.
• Cystatin C and beta trace protein demonstrate greater reliability as eGFR markers when FF varies.
• These findings have implications for selecting appropriate eGFR markers in pediatric renal disease management.