title: Improved equations estimating GFR in children with chronic kidney disease using an immunonephelometric determination of cystatin C.
abstract: The Chronic Kidney Disease in Children study is a cohort of about 600 children with chronic kidney disease (CKD) in the United States and Canada. The independent variable for our observations was a measurement of glomerular filtration rate(GFR) by iohexol disappearance (iGFR) at the first two visits 1 year apart and during alternate years thereafter. In a previous report, we had developed GFR estimating equations utilizing serum creatinine, blood urea nitrogen, height, gender, and cystatin C measured by an immunoturbidimetric method; however, the correlation coefficient of cystatin C and GFR(0.69) was less robust than expected. Therefore, 495 samples were re-assayed using immunonephelometry. The reciprocal of immunonephelometric cystatin C was as well correlated with iGFR as was height/serum creatinine (both 0.88). We developed a new GFR estimating equation using a random 2/3 of 965 person-visits and applied it to the remaining 1/3 as a validation data set. In the validation dataset, the correlation of the estimated GFR with iGFR was 0.92 with high precision and no bias; 91 and 45% of eGFR values were within 30 and 10% of iGFR, respectively. This equation works well in children with CKD in a range of GFR from 15 to 75 ml/min per 1.73 m2. Further studies are needed to establish the applicability to children of normal stature and muscle mass, and higher GFR.
authors.affiliation: University of Rochester School of Medicine, Rochester, NY, USA. george_schwartz@urmc.rochester.edu
authors.forename: George J
authors.initials: GJ
authors.lastname: Schwartz
authors.forename: Michael F
authors.initials: MF
authors.lastname: Schneider
authors.forename: Paula S
authors.initials: PS
authors.lastname: Maier
authors.forename: Marva
authors.initials: M
authors.lastname: Moxey-Mims
authors.forename: Vikas R
authors.initials: VR
authors.lastname: Dharnidharka
authors.forename: Bradley A
authors.initials: BA
authors.lastname: Warady
authors.forename: Susan L
authors.initials: SL
authors.lastname: Furth
authors.forename: Alvaro
authors.initials: A
authors.lastname: Muñoz
mesh_terms: D000293:Adolescent; D015415:Biomarkers / Q000097:blood; D001806:Blood Urea Nitrogen; D001827:Body Height; D002170:Canada; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D003287:Contrast Media; D003404:Creatinine / Q000097:blood; D055316:Cystatin C / Q000097:blood*; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007118:Immunoassay; D007223:Infant; D007472:Iohexol; D007668:Kidney / Q000378:metabolism / Q000503:physiopathology*; D016014:Linear Models; D008297:Male; D008954:Models, Biological; D015999:Multivariate Analysis; D009391:Nephelometry and Turbidimetry; D011237:Predictive Value of Tests; D051436:Renal Insufficiency, Chronic / Q000097:blood / Q000175:diagnosis* / Q000503:physiopathology; D015203:Reproducibility of Results; D013997:Time Factors; D014481:United States
chemical_list: D015415:Biomarkers; C525030:CST3 protein, human; D003287:Contrast Media; D055316:Cystatin C; D007472:Iohexol; D003404:Creatinine