title: Usefulness of serum cystatin C to determine the dose of vancomycin in neonate.
abstract: OBJECTIVE
  The vancomycin dosage regimen is regularly modified according to the patient's glomerular filtration rate (GFR). In the present study, we aimed to assess the usefulness of serum cystatin C (Cys-C) concentration, compared with serum creatinine (SCr) concentration, for predicting vancomycin clearance (CLvcm) in neonates.
  
  
  METHODS
  We retrospectively analyzed the laboratory data of 50 term neonates who were admitted to the neonatal intensive care unit and received intravenous vancomycin, and assessed the pharmacokinetic profiles. Creatinine clearance (CLcr) and GFR based on Cys-C (GFRcys-c) were estimated using the Schwartz and Larsson formulas, respectively.
  
  
  RESULTS
  The mean CLvcm (±standard deviation) was 74.52±31.17 L/hr, the volume of distribution of vancomycin was 0.67±0.14 L, and vancomycin half-life was 9.16±17.42 hours. The SCr was 0.46±0.25 mg/dL and serum Cys-C was 1.43±0.34 mg/L. The peak and trough concentrations of vancomycin were 24.65±14.84 and 8.10±5.35 mcg/mL, respectively. The calculated GFR based on serum creatinine concentration (GFR-Cr) and GFRcys-c were 70.2±9.45 and 63.6±30.18 mL/min, respectively. The correlation constant for CLvcm and the reciprocal of Cys-C (0.479, P=0.001) was significantly higher than that for CLvcm and the reciprocal of SCr (0.286, P=0.044). GFRcys-c was strongly correlated with CLvcm (P=0.001), and the correlation constant was significantly higher than that for CLvcm and CLcr (0.496, P=0.001). Linear regression analysis showed that only GFRcys-c was independently and positively correlated with CLvcm (F=41.9, P<0.001).
  
  
  CONCLUSIONS
  The use of serum Cys-C as a marker of CLvcm could be beneficial for more reliable predictions of serum vancomycin concentrations, particularly in neonates.
authors.affiliation: Department of Pediatrics, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: Jeong Eun
authors.initials: JE
authors.lastname: Shin
authors.affiliation: Department of Pediatrics, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: Soon Min
authors.initials: SM
authors.lastname: Lee
authors.affiliation: Department of Pediatrics, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: Ho Seon
authors.initials: HS
authors.lastname: Eun
authors.affiliation: Department of Pediatrics, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: Min Soo
authors.initials: MS
authors.lastname: Park
authors.affiliation: Department of Pediatrics, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: Kook In
authors.initials: KI
authors.lastname: Park
authors.affiliation: Department of Pediatrics, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: Ran
authors.initials: R
authors.lastname: Namgung
keywords: Clearance; Cystatin C; Vancomycin