Which creatinine and cystatin C equations can be reliably used in children?
OBJECTIVE
Estimation of GFR in children is challenging; reference methods are cumbersome, and formulas have limitations. The aims of this study were to evaluate (1) the new creatinine-based formula recently proposed by Schwartz using a kinetic colorimetric compensated Jaffe technique; (2) some cystatin C-derived formulas (Hoek, Le Bricon, Larsson, Rule, Filler, and Zappitelli) using a nephelemetric technique; and (3) combined formulas using both cystatin and creatinine (Zappitelli and Bouvet).


METHODS
These formulas were evaluated in a cross-sectional cohort of 252 children with moderate CKD or normal GFR, in comparison with the reference standard (inulin clearance, iGFR). Mean age, body weight, height, creatinine, and cystatin C were 10.7 ± 4.0 years, 35 ± 15 kg, 137 ± 20 cm, 55 ± 30 μmol/L, and 0.91 ± 0.35 mg/L, respectively.


RESULTS
Mean ± SD iGFR was 101 ± 32 ml/min per 1.73 m². When evaluating agreement between these formulas and iGFR (e.g. correlation, Bland Altman plots, bias, and accuracies), there was a good correlation between iGFR and all Le Bricon, Larsson, Rule, and Zappitelli (both) and locally adapted Schwartz and 2009 Schwartz formulas; by contrast, Filler and original 1976 Schwartz formulas overestimated iGFR, whereas Hoek and Bouvet formulas underestimated iGFR.


CONCLUSIONS
Different cystatin C-derived formulas (at least Larsson and Le Bricon) for estimating GFR as well as the Zappitelli combined formula are accurate in addition to the new Schwartz bedside formula in a general pediatric population.
Centre de Référence des Maladies Rénales Rares, Service de Néphrologie et Rhumatologie Pédiatriques Hôpital Femme Mère Enfant, Boulevard Pinel, 69677 Bron Cedex, France. justine.bacchetta@chu-lyon.fr
Justine
J
Bacchetta
Pierre
P
Cochat
Nicolas
N
Rognant
Bruno
B
Ranchin
Aoumeur
A
Hadj-Aissa
Laurence
L
Dubourg
D000293:Adolescent; D000367:Age Factors; D000704:Analysis of Variance; D015415:Biomarkers / Q000097:blood; D001827:Body Height; D001835:Body Weight; D016009:Chi-Square Distribution; D002648:Child; D003124:Colorimetry; D003404:Creatinine / Q000097:blood*; D003430:Cross-Sectional Studies; D055316:Cystatin C / Q000097:blood*; D005260:Female; D005602:France; D005919:Glomerular Filtration Rate; D006801:Humans; D007444:Inulin; D007674:Kidney Diseases / Q000097:blood / Q000175:diagnosis* / Q000503:physiopathology; D008297:Male; D008954:Models, Biological; D009391:Nephelometry and Turbidimetry; D011237:Predictive Value of Tests; D011446:Prospective Studies; D015203:Reproducibility of Results; D012737:Sex Factors
D015415:Biomarkers; C525030:CST3 protein, human; D055316:Cystatin C; D007444:Inulin; D003404:Creatinine