title: New standardized cystatin C and creatinine GFR equations in children validated with inulin clearance.
abstract: BACKGROUND
  This study compares glomerular filtration rate (GFR) equations in children based on standardized cystatin C (CYSC) and creatinine (CREA) and their combinations with renal clearance of inulin (C-inulin).
  
  
  METHODS
  A total of 220 children with different renal disorders were referred for C-inulin (median 84 ml/min/1.73 m(2)). Bias, precision (interquartile range, IQR), and accuracy (percentage of estimates ±30 % of C-inulin; P30) were evaluated for two cystatin C equations, CAPACYSC and BergCYSC, for creatinine equations, SchwartzCREA and GaoCREA, the arithmetic mean of CAPACYSC and SchwartzCREA (MEANCAPA+Schwartz), BergCYSC and SchwartzCREA (MEANBERG+SCHWARTZ) and the composite equation ChehadeCYSC+CREA.
  
  
  RESULTS
  Overall results of CAPACYSC, BergCYSC, SchwartzCREA, GaoCREA, MEANCAPA+Schwartz, MEANBERG+SCHWARTZ and ChehadeCYSC+CREA were: median bias -7.6/-4.9/-3.7/-2.3/-4.6/-4.0/-10.1 %, IQR 20.0/19.9/21.7/22.4/21.0/20.9/23.3 ml/min/1.73 m(2) and P30 86/86/80/83/89/91/83 %. The cystatin C equations, MEANCAPA+Schwartz and MEANBERG+SCHWARTZ had a more stable performance across subgroups compared with SchwartzCREA, GaoCREA and ChehadeCYSC+CREA.
  
  
  CONCLUSIONS
  Cystatin C was the preferred filtration marker for GFR estimation in children, while the benefit of combining cystatin C and creatinine deserves further investigations.
authors.affiliation: Department of Clinical Science, Intervention and Technology, Division of Pediatrics, Karolinska Institutet, Karolinska University Hospital Huddinge, 14186, Stockholm, Sweden, ulla.berg@ki.se.
authors.forename: Ulla B
authors.initials: UB
authors.lastname: Berg
authors.forename: Ulf
authors.initials: U
authors.lastname: Nyman
authors.forename: Rune
authors.initials: R
authors.lastname: Bäck
authors.forename: Magnus
authors.initials: M
authors.lastname: Hansson
authors.forename: Kajsa Åsling
authors.initials: KÅ
authors.lastname: Monemi
authors.forename: Maria
authors.initials: M
authors.lastname: Herthelius
authors.forename: Jonas
authors.initials: J
authors.lastname: Björk
mesh_terms: D000293:Adolescent; D015415:Biomarkers / Q000097:blood; D002648:Child; D002675:Child, Preschool; D003404:Creatinine / Q000097:blood*; D055316:Cystatin C / Q000097:blood*; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007328:Insulin / Q000097:blood; D007677:Kidney Function Tests / Q000379:methods / Q000592:standards*; D008297:Male
chemical_list: D015415:Biomarkers; C525030:CST3 protein, human; D055316:Cystatin C; D007328:Insulin; D003404:Creatinine