title: Implications of serum creatinine measurements on GFR estimation and vancomycin dosing in children.
abstract: BACKGROUND
  Different serum creatinine (sCr) assays may obtain different values in the same patient, causing discrepancies in estimated glomerular filtration rate (eGFR) and sCr-based vancomycin dosing calculations.
  
  
  OBJECTIVE
  To identify potential discrepancies in sCr concentrations obtained by different assays, the compensated Jaffe (sCr-Jaffe) and the enzymatic (sCr-enz), and to compare between the eGFR and vancomycin daily dose, based on these sCr values.
  
  
  METHODS
  sCr-Jaffe and, sCr-enz concentrations of 890 healthy children, aged 1-18 years, were available from the Canadian Laboratory Initiative in Pediatric Reference Intervals study in Ontario. For each subject, eGFR (eGFR-Jaffe, eGFR-enz) was calculated using the revised Schwartz equation, and vancomycin daily dose (Vdose-Jaffe, Vdose-enz) was calculated using a sCr-based pharmacokinetic model.
  
  
  RESULTS
  Significant, age-related differences were found in sCr concentrations, and in subsequent eGFR and Vdose, between the two assays. In children aged 1-5 years, mean sCr-Jaffe was higher than sCr-enz (44.0 ± 5.0 vs. 27.7 ± 7.3 μmol/L, P < 0.001), leading to lower eGFR-Jaffe (83.2 ± 9.0 vs. 137.9 ± 27.1 mL/min/1.73m2, P < 0.001) and lower Vdose-Jaffe (44.7 ± 2.5 vs. 53.5 ± 5.1 mg/kg/24 h, P < 0.001).
  
  
  CONCLUSIONS
  Based on these findings, young children may be at risk for vancomycin under-treatment. Further research is needed to define the more accurate sCr assay in young children treated with renally excreted drugs.
authors.affiliation: Division of Clinical Pharmacology & Toxicology, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Gal
authors.initials: G
authors.lastname: Neuman
authors.forename: Irena
authors.initials: I
authors.lastname: Nulman
authors.forename: Khosrow
authors.initials: K
authors.lastname: Adeli
authors.forename: Gideon
authors.initials: G
authors.lastname: Koren
authors.forename: David A
authors.initials: DA
authors.lastname: Colantonio
authors.forename: Anders
authors.initials: A
authors.lastname: Helldén
mesh_terms: D000293:Adolescent; D041923:Adolescent Development; D000900:Anti-Bacterial Agents / Q000008:administration & dosage* / Q000097:blood / Q000493:pharmacokinetics; D002648:Child; D002657:Child Development; D002675:Child, Preschool; D015331:Cohort Studies; D003404:Creatinine / Q000097:blood*; D054796:Drug Dosage Calculations; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007223:Infant; D007668:Kidney / Q000254:growth & development / Q000378:metabolism* / Q000502:physiology / Q000503:physiopathology; D008297:Male; D008954:Models, Biological; D009864:Ontario; D065667:Renal Elimination; D051437:Renal Insufficiency / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D014640:Vancomycin / Q000008:administration & dosage* / Q000097:blood / Q000493:pharmacokinetics
chemical_list: D000900:Anti-Bacterial Agents; D014640:Vancomycin; D003404:Creatinine
keywords: dosing guidelines; laboratory medicine; pharmacokinetics; renal drug clearance