title: Cystatin C--a new marker of glomerular filtration rate in children independent of age and height.
abstract: OBJECTIVE
  Serum creatinine is the most common endogenous marker of renal function. The proportionality between creatinine production and muscle mass requires adjustment for height and body composition. The low molecular weight protein cystatin C is produced by all nucleated cells and eliminated by glomerular filtration. Therefore, cystatin C was studied as an alternative marker of glomerular filtration rate (GFR) in children.
  
  
  METHODS
  Cystatin C and creatinine were measured in sera from inulin clearance (CIn) examinations performed in 184 children aged 0.24 to 17.96 years. CIn ranged from 7 to 209 mL/min/1.73 m (median, 77).
  
  
  RESULTS
  The reciprocal of cystatin C correlated better with CIn (r = 0.88) than the reciprocal of creatinine (r = 0.72). Stepwise regression analysis identified no covariates for the correlation between cystatin C and CIn, whereas height was a covariate for creatinine. Using an estimate of GFR from serum creatinine and height, correlation with CIn was similar to cystatin C, but female gender and dystrophy were associated with an overestimation of GFR. Diagnostic accuracy in the identification of reduced GFR measured as area under the receiver-operating characteristic plot was 0.970 +/- 0.135 (mean +/- SE) for cystatin C and 0.894 +/- 0.131 for creatinine (NS). A cutoff cystatin C concentration of 1.39 mg/L had 90% sensitivity and 86% specificity for detecting abnormal GFR.
  
  
  CONCLUSIONS
  Unlike creatinine, serum cystatin C reflects renal function in children independent of age, gender, height, and body composition.
authors.affiliation: Children's Hospital of Hannover Medical School, Hannover Medical School, Hannover, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Bökenkamp
authors.forename: M
authors.initials: M
authors.lastname: Domanetzki
authors.forename: R
authors.initials: R
authors.lastname: Zinck
authors.forename: G
authors.initials: G
authors.lastname: Schumann
authors.forename: D
authors.initials: D
authors.lastname: Byrd
authors.forename: J
authors.initials: J
authors.lastname: Brodehl
mesh_terms: D000293:Adolescent; D000367:Age Factors; D001823:Body Composition; D001827:Body Height; D002648:Child; D002675:Child, Preschool; D003404:Creatinine / Q000097:blood; D055316:Cystatin C; D015891:Cystatins / Q000097:blood*; D015853:Cysteine Proteinase Inhibitors / Q000097:blood*; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007223:Infant; D007444:Inulin / Q000378:metabolism; D007668:Kidney / Q000502:physiology*; D016014:Linear Models; D008297:Male; D012680:Sensitivity and Specificity
chemical_list: C525030:CST3 protein, human; D055316:Cystatin C; D015891:Cystatins; D015853:Cysteine Proteinase Inhibitors; D007444:Inulin; D003404:Creatinine