title: Childhood Estimates of Glomerular Filtration Rate Based on Creatinine and Cystatin C: Importance of Body Composition.
abstract: BACKGROUND
  Creatinine and cystatin C concentrations are commonly used to estimate glomerular filtration rate (eGFR) in clinical practice and epidemiological studies. To estimate the influence of different body composition measures on eGFR from creatinine and cystatin C blood concentrations, we compared the associations of different anthropometric and body composition measures with eGFR derived from creatinine (eGFRcreat) and cystatin C (eGFRcystC) blood concentrations.
  
  
  METHODS
  In a population-based cohort study among 4,305 children aged 6.0 years (95% range 5.7-8.0), we measured weight and height and calculated body mass index (BMI) and body surface area (BSA), and lean and fat mass using dual-energy X-ray absorptiometry. At the same age, we measured creatinine and cystatin C blood concentrations and estimated the GFR.
  
  
  RESULTS
  Correlation between eGFR based on creatinine and cystatin C concentrations was r = 0.40 (p value <0.01). Higher BMI was associated with lower eGFRcystC but not with eGFRcreat. Higher BSA was associated with higher eGFRcreat and lower eGFRcystC (p value <0.05). Lean and fat mass percentages were associated with eGFRcreat but not with eGFRcystC.
  
  
  CONCLUSIONS
  Our findings suggest that both eGFRcreat and eGFRcystC are influenced by BMI and BSA. eGFRcreat is more strongly influenced by body composition than eGFRcystC.
authors.affiliation: The Generation R Study Group, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands.
authors.forename: Kozeta
authors.initials: K
authors.lastname: Miliku
authors.forename: Hanneke
authors.initials: H
authors.lastname: Bakker
authors.forename: Eiske M
authors.initials: EM
authors.lastname: Dorresteijn
authors.forename: Karlien
authors.initials: K
authors.lastname: Cransberg
authors.forename: Oscar H
authors.initials: OH
authors.lastname: Franco
authors.forename: Janine F
authors.initials: JF
authors.lastname: Felix
authors.forename: Vincent W V
authors.initials: VW
authors.lastname: Jaddoe
mesh_terms: D015502:Absorptiometry, Photon; D001823:Body Composition / Q000502:physiology*; D015992:Body Mass Index; D001830:Body Surface Area; D002648:Child; D002675:Child, Preschool; D003404:Creatinine / Q000097:blood*; D055316:Cystatin C / Q000097:blood*; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007677:Kidney Function Tests; D008297:Male; D011446:Prospective Studies
chemical_list: C525030:CST3 protein, human; D055316:Cystatin C; D003404:Creatinine