Hyperfiltration affects accuracy of creatinine eGFR measurement.
OBJECTIVE
Surrogate markers such as creatinine, cystatin C (CysC), and beta trace protein (BTP) have been used to estimate GFR (eGFR). The accuracy of eGFR may be altered with hyperfiltration and differences in filtration fraction (FF). It is hypothesized that the accuracy of creatinine for eGFR may be affected by hyperfiltration and different effective renal plasma flow (ERPF).


METHODS
A total of 127 pediatric patients with various renal diseases underwent simultaneous measurements of GFR using 51Cr-EDTA renal scan and ERPF (131I-hippurate clearance) to calculate the FF (FF=GFR/ERPF). The eGFRs were calculated using the commonly used Schwartz (creatinine), Filler (CysC), and Benlamri (BTP) formulas. Agreement of the eGFRs with the measured isotope GFRs was assessed by Bland-Altman plots. Correlation analysis was performed using nonparametric tests to compare FF with eGFR-GFR.


RESULTS
The 127 children at a median age (with 25th percentile, 75th percentile) of 11.9 (8.5, 14.9) years had a mean 51Cr EDTA-GFR of 100.6±32.1 ml/min per 1.73 m2 and a median 131I-hippurate clearance (ERPF) of 588 (398,739) ml/min per 1.73 m2. Mean FF was 17.7±4.5% with no correlation between the FF and the error (eGFR-GFR) for CysC and BTP eGFR, whereas there was a significant negative correlation between the error for Schwartz eGFR and FF.


CONCLUSIONS
There is a significant negative correlation between the error for the Schwartz eGFR and the FF. CysC and BTP are not affected by differences in FF.
Department of Pediatrics, Children's Hospital, London Health Sciences Centre, Schulich School of Medicine and Dentistry, University of Western Ontario, 800 Commissioner's Road East, Room E6-104, London ON, Canada, N6A 5W9.
Shih-Han S
SH
Huang
Ajay P
AP
Sharma
Abeer
A
Yasin
Robert M
RM
Lindsay
William F
WF
Clark
Guido
G
Filler
D000293:Adolescent; D015415:Biomarkers / Q000097:blood; D002648:Child; D002860:Chromium Radioisotopes; D003404:Creatinine / Q000097:blood*; D055316:Cystatin C / Q000097:blood; D004492:Edetic Acid; D005260:Female; D005919:Glomerular Filtration Rate; D006626:Hippurates; D006801:Humans; D019746:Intramolecular Oxidoreductases / Q000097:blood; D007457:Iodine Radioisotopes; D007668:Kidney / Q000378:metabolism / Q000503:physiopathology*; D007674:Kidney Diseases / Q000097:blood / Q000175:diagnosis* / Q000503:physiopathology; D007677:Kidney Function Tests; D054834:Lipocalins / Q000097:blood; D008297:Male; D008954:Models, Biological; D009864:Ontario; D011237:Predictive Value of Tests; D017596:Renal Plasma Flow, Effective; D015203:Reproducibility of Results
D015415:Biomarkers; C525030:CST3 protein, human; D002860:Chromium Radioisotopes; D055316:Cystatin C; D006626:Hippurates; D007457:Iodine Radioisotopes; D054834:Lipocalins; D004492:Edetic Acid; D003404:Creatinine; D019746:Intramolecular Oxidoreductases; C022466:prostaglandin R2 D-isomerase