title: Is serum cystatin C the marker of choice to predict glomerular filtration rate in paediatric patients?
abstract: BACKGROUND
  It has been suggested that serum cystatin C (cyst-C) concentration provides a better indication of changes in glomerular filtration rate (GFR) than does serum creatinine concentration.
  
  
  METHODS
  Because of conflicting results as to the usefulness of cyst-C, we compared the GFRs calculated from serum cyst-C, inulin clearance and endogenous creatinine clearance in children. GFRs calculated from cystatin concentration, inulin clearance following a single injection and endogenous creatinine clearance using Jaffé and enzymic methods were compared in 66 children (1.3-21.9 years) with a variety of renal disorders. Receiver operating curve analysis was used to determine the cut-off value that would give the best discrimination between normal and decreased GFR.
  
  
  RESULTS
  The serum cyst-C concentration ranged from 0.66 to 7.61 mg/L (median 1.94). Serum creatinine Jaffé concentration (creat-J) ranged from 38 to 871 micro mol/L (median 105) and creatinine enzymatic concentration (creat-E) ranged from 28 to 862 micro mol/L (median 126). The linear correlation coefficient (R) of 1/cyst-C versus GFR (R = 0.937) did not differ from either that of 1/creat-J versus GFR (R = 0.918) or that of 1/creat-E versus GFR (R = 0.901). These coefficients had overlapping confidence intervals. The areas under the curve for cyst-C, creat-J and creat-E were 0.967, 0.977 and 0.924, respectively, and were not significantly different from each other. For cyst-C, the optimal cut-off was 1.1 mg/L.
  
  
  CONCLUSIONS
  Serum cyst-C is equivalent to creat-J and creat-E as a marker for estimating the GFR in the paediatric population studied.
authors.affiliation: Department of Clinical Chemistry, University Medical Centre, Nijmegen, The Netherlands. J.Willems@akc.umcn.nl
authors.forename: Hans L
authors.initials: HL
authors.lastname: Willems
authors.forename: Luuk B
authors.initials: LB
authors.lastname: Hilbrands
authors.forename: John F
authors.initials: JF
authors.lastname: van de Calseyde
authors.forename: Leo A H
authors.initials: LA
authors.lastname: Monnens
authors.forename: Dorine W
authors.initials: DW
authors.lastname: Swinkels
mesh_terms: D000293:Adolescent; D000328:Adult; D002624:Chemistry, Clinical / Q000379:methods*; D002648:Child; D002675:Child, Preschool; D003404:Creatinine / Q000097:blood; D055316:Cystatin C; D015891:Cystatins / Q000097:blood*; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007223:Infant; D008297:Male; D012680:Sensitivity and Specificity
chemical_list: C525030:CST3 protein, human; D055316:Cystatin C; D015891:Cystatins; D003404:Creatinine