title: Measurements of serum cystatin C concentrations underestimate renal dysfunction in pediatric patients with chronic kidney disease.
abstract: BACKGROUND
  In our clinical experience, cystatin C (CysC) concentrations are not as high as expected in patients with chronic kidney disease (CKD) and high-stage renal dysfunction. We therefore investigated whether measurements of serum CysC result in an underestimation of renal dysfunction in pediatric patients with CKD.
  
  
  METHODS
  Glomerular filtration rate (GFR) was estimated from serum creatinine (Cr) concentration, using the equation Cr-GFR (%) = [0.30 × body length (m)/serum Cr] × 100; and from serum CysC concentration, using the equation Cys-GFR (%) = (0.70/serum CysC) × 100. We investigated the relationship between GFR estimated by these 2 equations. Patients aged 2-12 years were assorted into 5 groups, based on GFR-Cr categories of <12.5, ≥12.5 to <25, ≥25 to <50, ≥50 to <75, and ≥75%, and GFR-CysC/GFR-Cr ratios were compared in these 5 groups.
  
  
  RESULTS
  The median GFR-CysC/GFR-Cr ratio in groups of patients with GFR-Cr of <12.5, ≥12.5 to <25, ≥25 to <50, ≥50 to <75, and ≥75% were 2.28, 1.48, 1.22, 1.18 and 0.98, respectively, with statistically significant differences between any two groups (p < 0.001).
  
  
  CONCLUSIONS
  Measurements of serum CysC concentrations lead to underestimation of renal dysfunction in pediatric patients with CKD.
authors.affiliation: Department of Pediatric Nephrology, Aichi Children's Health and Medical Center, 1-2 Osakada, Morioka-cho, Obu, Aichi 474-8710, Japan. o_uemura@hkg.odn.ne.jp
authors.forename: Osamu
authors.initials: O
authors.lastname: Uemura
authors.forename: Katsumi
authors.initials: K
authors.lastname: Ushijima
authors.forename: Takuhito
authors.initials: T
authors.lastname: Nagai
authors.forename: Takuji
authors.initials: T
authors.lastname: Yamada
authors.forename: Satoshi
authors.initials: S
authors.lastname: Yamakawa
authors.forename: Yoshiko
authors.initials: Y
authors.lastname: Hibi
authors.forename: Hideki
authors.initials: H
authors.lastname: Hayakawa
authors.forename: Yayoi
authors.initials: Y
authors.lastname: Nabeta
authors.forename: Yoshiko
authors.initials: Y
authors.lastname: Shinkai
authors.forename: Kouichi
authors.initials: K
authors.lastname: Koike
authors.forename: Masaki
authors.initials: M
authors.lastname: Kuwabara
mesh_terms: D002648:Child; D002675:Child, Preschool; D003404:Creatinine / Q000097:blood; D055316:Cystatin C / Q000097:blood*; D005188:False Negative Reactions; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007668:Kidney / Q000503:physiopathology; D007676:Kidney Failure, Chronic / Q000097:blood* / Q000503:physiopathology; D008297:Male; D055641:Mathematical Concepts; D051436:Renal Insufficiency, Chronic / Q000097:blood* / Q000503:physiopathology
chemical_list: D055316:Cystatin C; D003404:Creatinine