Comparing creatinine-estimated and cystatin C-estimated glomerular filtration rates in children with a congenital solitary kidney

Czech version

Authors: H. Flögelová ¹; J. Prošková ²; K. Langová ³; D. Dvořák ¹
Authors‘ workplace: Dětská klinika, Lékařská fakulta Univerzity Palackého v Olomouci a Fakultní nemocnice Olomouc ¹; Oddělení klinické biochemie, Fakultní nemocnice Olomouc ²; Ústav lékařské biofyziky, Lékařská fakulta Univerzity Palackého v Olomouci ³
Published in: Čes-slov Pediat 2021; 76 (7): 368-372.
Category: Original Papers

Overview

Introduction and aim of the study: During their lives, people with a solitary kidney develop hyperfiltration damaging the kidney and results in decreased renal function. Reduced Schwartz-estimated GFR is a relatively late marker of renal damage. According to some authors, an earlier marker of subclinical damage to the solitary kidney is serum cystatin C. The study aimed to determine whether in children with a congenital solitary/solitary functioning kidney (SFK), cystatin C-estimated GFR is significantly lower than creatinine-estimated GFR.

Methods: A prospective study assessed GFRs in 70 children aged 2–18 years (mean 9.1 years; 49 boys) with a SFK due to unilateral agenesis or multicystic dysplasia. Excluded were children with SFK and additional CAKUT or a history of febrile UTI. Serum creatinine (μmol/L) was measured using the enzymatic method. Cystatin C (mg/L) was measured with an immunoturbidimetric assay. A difference was determined between GFRs estimated with the following formulae:

Schwarz-estimated GFR: height in cm x 0.6/creatinine

Cystatin C-estimated GFR: 1.178 x (S_cyst)^-0.931

For statistical analyses, the paired t-test, non-parametric Wilcoxon test and Bland-Altman plot were used.

Results: The mean Schwartz- and cystatin C-estimated GFRs were 1.639 (SD 0.295) and 1.268 (SD 0.196) mL/s/1.73 m², respectively; a statistically significant difference (p<0.0001). The Bland-Altman plot suggested that the difference between the two methods depended on the GFR; the higher the GFR, the greater the difference.

Conclusions: In children with an intact solitary kidney (normal GFR to CKD II), cystatin C-estimated GFR was significantly lower than Schwartz-estimated GFR. Since the difference was GFR-dependent, it cannot be concluded that in children with a solitary kidney, reduced cystatin C-estimated GFR is an adequate early marker of subclinical renal damage.

Keywords:

Creatinine – Glomerular filtration rate – cystatin C – solitary kidney

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