title: Longitudinal analysis of serum cystatin C for estimating the glomerular filtration rate in preterm infants.
abstract: BACKGROUND
  Cystatin C (Cys-C) is a more sensitive marker of renal function than creatinine (Cre) in pediatric and adult populations. However, the reference values of serum Cys-C for estimating glomerular filtration rates (eGFRs) in premature infants during the first year of life have not been sufficiently studied.
  
  
  METHODS
  In this prospective study, 481 blood samples were collected from 261 preterm infants with uncomplicated clinical courses during their first year of life. Infants were divided into three groups according to gestational age at birth: 27-30 weeks, 31-33 weeks, and 34-36 weeks. Serum Cys-C and Cre levels were measured at 6-30 days, 3-5 months, 7-9 months, and 12-14 months after birth and the eGFR was calculated using two previously published equations.
  
  
  RESULTS
  The median serum Cys-C levels were 1.776, 1.248, 1.037, and 0.960 mg/L at the first, second, third, and fourth measurement time-point, respectively, with the value significantly decreasing with age up to 12-14 months. Cys-C levels were independent of gestational age and gender. In contrast to Cys-C, serum Cre values declined rapidly up to 3-5 months, then remained constant up to 12-14 months. Using the Cys-C-based equation, the eGFR significantly increased with increasing age until approximately 1 year after birth; however, no such trend was noted using the equation based on Cys-C + Cre.
  
  
  CONCLUSIONS
  Reference ranges for Cys-C in premature infants decline gradually over the first year after birth. Cys-C appears to be a more reliable marker than Cre for estimating GFR in preterm infants.
authors.affiliation: Department of Pediatrics, Kitakyushu Municipal Medical Center, Fukuoka, Japan. binki@nifty.com.|Department of Pediatrics, National Hospital Organization Kokura Medical Center, 10-1 Harugaoka, Kokuraminami-ku, Kiakyushu-shi, Fukuoka, Japan. binki@nifty.com.
authors.forename: Toshinori
authors.initials: T
authors.lastname: Nakashima
authors.affiliation: Department of Pediatrics, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
authors.forename: Hirosuke
authors.initials: H
authors.lastname: Inoue
authors.affiliation: Department of Pediatrics, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
authors.forename: Junko
authors.initials: J
authors.lastname: Fujiyoshi
authors.affiliation: Department of Pediatrics, Kitakyushu Municipal Medical Center, Fukuoka, Japan.
authors.forename: Naoko
authors.initials: N
authors.lastname: Matsumoto
mesh_terms: D015415:Biomarkers / Q000097:blood; D003404:Creatinine / Q000097:blood*; D055316:Cystatin C / Q000097:blood*; D005260:Female; D005865:Gestational Age; D005919:Glomerular Filtration Rate; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007234:Infant, Premature / Q000097:blood / Q000502:physiology*; D007677:Kidney Function Tests / Q000379:methods*; D008137:Longitudinal Studies; D008297:Male; D011446:Prospective Studies; D012016:Reference Values
chemical_list: D015415:Biomarkers; D055316:Cystatin C; D003404:Creatinine
keywords: Longitudinal analysis; Preterm infants; Reference ranges; Renal function; Serum creatinine; Serum cystatin C
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