title: Reference ranges for plasma cystatin C and creatinine measurements in premature infants, neonates, and older children.
abstract: OBJECTIVE
  To establish a reference range in the paediatric population for the new glomerular filtration rate (GFR) marker, cystatin C, and to compare it with that of creatinine.
  
  
  METHODS
  Cystatin C and creatinine were measured by particle enhanced nephelometric immunoassay (PENIA) and fixed interval Jaff¿e methods, respectively, in 291 children aged 1 day to 17 years, including 30 premature infants with gestational ages ranging from 24 to 36 weeks.
  
  
  RESULTS
  In the premature infants, concentrations of both cystatin C and creatinine were significantly raised compared with term infants, with cystatin C concentrations being between 1.10 and 2.06 mg/litre and creatinine between 32 and 135 micromol/litre. In premature infants, there was no significant relation between gestational age and cystatin C or creatinine concentration. Creatinine concentrations fell to a nadir at 4 months of age, rising gradually to adult values by about 15-17 years of age, in contrast to cystatin C, which fell to a mean concentration of 0.80 mg/litre by the 1st year of life, and remained constant throughout adulthood up to the age of 50 years. Neither analyte showed any influence of sex.
  
  
  CONCLUSIONS
  The measurement of cystatin C, rather than creatinine, is more practical for monitoring GFR changes in the paediatric population.
authors.affiliation: Department of Clinical Biochemistry, St Bartholomew's and The Royal London, School of Medicine and Dentistry, Turner Street, London E1 2AD, UK. h.finney@mds.qmw.ac.uk
authors.forename: H
authors.initials: H
authors.lastname: Finney
authors.forename: D J
authors.initials: DJ
authors.lastname: Newman
authors.forename: H
authors.initials: H
authors.lastname: Thakkar
authors.forename: J M
authors.initials: JM
authors.lastname: Fell
authors.forename: C P
authors.initials: CP
authors.lastname: Price
mesh_terms: D000293:Adolescent; D015415:Biomarkers / Q000097:blood; D002648:Child; D002675:Child, Preschool; D003404:Creatinine / Q000097:blood*; D015891:Cystatins / Q000097:blood*; D005919:Glomerular Filtration Rate / Q000502:physiology*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D009391:Nephelometry and Turbidimetry / Q000379:methods; D012016:Reference Values
chemical_list: D015415:Biomarkers; D015891:Cystatins; D003404:Creatinine