title: Age- and sex-specific reference limits for creatinine, cystatin C and the estimated glomerular filtration rate.
abstract: BACKGROUND
  Early detection of patients with chronic kidney disease is of great importance. This study developed reference limits for serum creatinine and serum cystatin C concentrations and for the estimated glomerular filtration rate (eGFR) in healthy subjects from the general population aged 25-65 years.
  
  
  METHODS
  This study defined a reference population including 985 subjects from the first follow-up of the Study of Health in Pomerania. Serum creatinine was measured with a modified kinetic Jaffé method. Serum cystatin C was measured with a nephelometric assay. The eGFR was calculated from serum creatinine according to the Cockcroft-Gault (eGFR(CG)) and the Modification of Diet in Renal Disease (eGFR(MDRD)) equation, respectively, as well as from serum cystatin C according to the formula by Larsson (eGFR(Larsson)). Non-parametric quantile regression was used to estimate the reference limits. For serum creatinine and serum cystatin C the 95th percentile and for eGFR(CG), eGFR(MDRD) and eGFR(Larsson) the 5th percentile were selected as reference limits. All data was weighted to reflect the age- and sex-structure of the German population in 2008.
  
  
  RESULTS
  The reference limits for serum creatinine (men: 1.11-1.23 mg/dL; women: 0.93-1.00 mg/dL) and serum cystatin C levels (men: 0.92-1.04 mg/L; women: 0.84-1.02 mg/L) increased with advancing age. The reference limits for eGFR decreased with increasing age (eGFR(CG) men: 106.0-64.7 mL/min, women 84.4-57.9 mL/min; eGFR(MDRD) men: 82.5-62.2 mL/min/1.73 m², women 75.0-58.2 mL/min/1.73 m²; eGFR(Larsson) men: 85.5-72.9 mL/min, women 94.5-75.7 mL/min).
  
  
  CONCLUSIONS
  This study presents age- and sex-specific reference limits for five measures of renal function based on quantile regression models.
authors.affiliation: Institute of Clinical Chemistry and Laboratory Medicine, Ernst-Moritz-Arndt-University Greifswald, Greifswald, Germany. anke.hannemann@uni-greifswald.de
authors.forename: Anke
authors.initials: A
authors.lastname: Hannemann
authors.forename: Nele
authors.initials: N
authors.lastname: Friedrich
authors.forename: Kathleen
authors.initials: K
authors.lastname: Dittmann
authors.forename: Christin
authors.initials: C
authors.lastname: Spielhagen
authors.forename: Henri
authors.initials: H
authors.lastname: Wallaschofski
authors.forename: Henry
authors.initials: H
authors.lastname: Völzke
authors.forename: Rainer
authors.initials: R
authors.lastname: Rettig
authors.forename: Karlhans
authors.initials: K
authors.lastname: Endlich
authors.forename: Uwe
authors.initials: U
authors.lastname: Lendeckel
authors.forename: Sylvia
authors.initials: S
authors.lastname: Stracke
authors.forename: Matthias
authors.initials: M
authors.lastname: Nauck
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D001774:Blood Chemical Analysis / Q000592:standards*; D003404:Creatinine / Q000097:blood*; D055316:Cystatin C / Q000097:blood*; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007677:Kidney Function Tests / Q000592:standards*; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D012044:Regression Analysis; D012737:Sex Factors
chemical_list: D055316:Cystatin C; D003404:Creatinine