Comparing different estimated glomerular filtration rate equations in assessing glomerular function in children based on creatinine and cystatin C.

BACKGROUND: Glomerular filtration rate (GFR) is the best marker used to assess renal function. Estimated GFR (eGFR) equations have been developed, and the ideal formula is still under discussion. We wanted to find the most practical and reliable GFR in eGFR formulas. We compared serum creatinine (Scr)- and cystatin C (cysC)-based eGFR formulas in the literature. We also aimed to determine the suitability and the reliability of cysC for practical use in determining GFR in children. METHODS: We have enrolled 238 children in the study. Measurement of 24-hour creatinine clearance was compared with eGFR equations which are based on Scr, cysC, and creatinine plus cysC. RESULTS: Of the patients (n = 238), 117 were males (49.2%), and 121 (50.8%) were females with a median age of 9.0 years. The areas under the ROC curves of Counahan-Barratt and Bedside Schwartz were equal and 0.89 (with a 95% CI 0.80-0.97). The areas under the ROC curves were not significantly different in all cystatin C-based eGFR equations. The highest AUC values for differentiating normal vs abnormal renal functions according to CrCl24 were for the CKiD-cysC and CKiD-Scr-cysC equations. CONCLUSIONS: In our study, compared with creatinine-based ones, the cystatin C-based formulas did not show much superiority in predicting eGFR. Still, we think Bedside Schwartz is a good formula to provide ease of use because, in this equation, the constant k is same for all age groups. However, the most valuable equations in determining chronic kidney disease are the CKiD-cysC and CKiD-Scr-cysC equations.