title: Simple cystatin C-based prediction equations for glomerular filtration rate compared with the modification of diet in renal disease prediction equation for adults and the Schwartz and the Counahan-Barratt prediction equations for children.
abstract: BACKGROUND
  Serum creatinine is the most commonly used marker for estimation of glomerular filtration rate (GFR). To compensate for its drawbacks as a GFR marker, several prediction equations including several parameters are being used, with the Modification of Diet in Renal Disease (MDRD), Schwartz, and Counahan-Barratt equations being the ones most widely accepted for estimation of relative GFR in mL x min(-1) x (1.73 m(2))(-1). The present study analyzes whether these GFR prediction equations for adults and children might be replaced by simple prediction equations based on plasma concentrations of cystatin C.
  
  
  METHODS
  Data from 536 patients (0.3-93 years), consecutively referred for determination of GFR by an invasive gold standard procedure, were used for the analysis. Calculations of bias (median percentage of error), correlation (adjusted R(2)), and percentage of estimates within 30% and 50% of measured GFR were used in the comparisons.
  
  
  RESULTS
  A cystatin C-based prediction equation using only concentration in mg/L and a prepubertal factor: GFR [mL x min(-1) x (1.73 m(2))(-1)] = 84.69 x cystatin C (mg/L)(-1.680) x 1.384 (if a child <14 years) assessed GFR equally well or better than the simplified MDRD, the Schwartz, and the Counahan-Barratt prediction equations for the adult (> or =18 years) and juvenile groups of the investigated cohort. Age did not influence the cystatin C-based prediction equation for adults, whereas gender did, but with a factor close to unity (0.948 for females).
  
  
  CONCLUSIONS
  A GFR prediction equation based solely on cystatin C (in mg/L) and a prepubertal factor might replace the simplified MDRD prediction equation for adults and the Schwartz and Counahan-Barratt prediction equations for children.
authors.affiliation: Department of Clinical Chemistry, Competence Centre for Clinical Research, Department of Nephrology, University Hospital, Lund, Sweden. anders.grubb@klinkem.lu.se
authors.forename: Anders
authors.initials: A
authors.lastname: Grubb
authors.forename: Ulf
authors.initials: U
authors.lastname: Nyman
authors.forename: Jonas
authors.initials: J
authors.lastname: Björk
authors.forename: Veronica
authors.initials: V
authors.lastname: Lindström
authors.forename: Bengt
authors.initials: B
authors.lastname: Rippe
authors.forename: Gunnar
authors.initials: G
authors.lastname: Sterner
authors.forename: Anders
authors.initials: A
authors.lastname: Christensson
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D015415:Biomarkers / Q000097:blood; D002648:Child; D002675:Child, Preschool; D055316:Cystatin C; D015891:Cystatins / Q000097:blood*; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007668:Kidney / Q000503:physiopathology*; D007674:Kidney Diseases / Q000175:diagnosis* / Q000178:diet therapy* / Q000503:physiopathology; D008297:Male; D008433:Mathematics; D008875:Middle Aged; D011237:Predictive Value of Tests; D012737:Sex Factors
chemical_list: D015415:Biomarkers; C525030:CST3 protein, human; D055316:Cystatin C; D015891:Cystatins