Correlation between cystatin C-based formulas, Schwartz formula and urinary creatinine clearance for glomerular filtration rate estimation in children with kidney disease.
BACKGROUND
Assessment of glomerular filtration rate (GFR) is an important tool for monitoring renal function.


OBJECTIVE
Regarding to limitations in available methods, we intended to calculate GFR by cystatin C (Cys C) based formulas and determine correlation rate of them with current methods.


METHODS
We studied 72 children (38 boys and 34 girls) with renal disorders. The 24 hour urinary creatinine (Cr) clearance was the gold standard method. GFR was measured with Schwartz formula and Cys C-based formulas (Grubb, Hoek, Larsson and Simple). Then correlation rates of these formulas were determined.


RESULTS
Using Pearson correlation coefficient, a significant positive correlation between all formulas and the standard method was seen (R(2) for Schwartz, Hoek, Larsson, Grubb and Simple formula was 0.639, 0.722, 0.705, 0.712, 0.722, respectively) (P<0.001). Cys C-based formulas could predict the variance of standard method results with high power. These formulas had correlation with Schwarz formula by R(2) 0.62-0.65 (intermediate correlation). Using linear regression and constant (y-intercept), it revealed that Larsson, Hoek and Grubb formulas can estimate GFR amounts with no statistical difference compared with standard method; but Schwartz and Simple formulas overestimate GFR.


CONCLUSIONS
This study shows that Cys C-based formulas have strong relationship with 24 hour urinary Cr clearance. Hence, they can determine GFR in children with kidney injury, easier and with enough accuracy. It helps the physician to diagnosis of renal disease in early stages and improves the prognosis.
Department of Pediatrics, Guilan University of Medical Sciences, Guilan, Iran.
Afshin
A
Safaei-Asl
Department of Pediatrics, Guilan University of Medical Sciences, Guilan, Iran.
Mercede
M
Enshaei
Department of Community Medicine, Guilan University of Medical Sciences, Guilan, Iran.
Abtin
A
Heydarzadeh
Department of Pediatrics, Guilan University of Medical Sciences, Guilan, Iran.
Shohreh
S
Maleknejad
Child; Creatinine; Cystatin C; Glomerular filtration rate; Kidney disease
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