title: Creatinine reference values in ELBW infants: impact of quantification by Jaffe or enzymatic method.
abstract: OBJECTIVE
  Serum creatinine (Scr) reflects to a certain extent glomerular filtration rate in neonates, but postnatal observations also depends on the technique used to quantify Scr (Jaffe colorimetry or enzymatic quantification).
  
  
  METHODS
  In an attempt to quantify differences between these techniques, we compared postnatal Scr trends in two consecutive cohorts of extremely low birth-weight (ELBW) neonates before and following a switch from uncompensated Jaffe to enzymatic Scr quantification. Postnatal Scr (Days 1, 2, 3, 4, 5, 6, 7, 8, 9, 14, 21, 28, and 42) in 151 ELBW neonates (uncompensated Jaffe) was compared to 116 more recently admitted ELBW neonates (enzymatic).
  
  
  RESULTS
  Although clinical characteristics were similar between both cohorts, median postnatal Jaffe Scr values were significantly higher compared to enzymatic quantification (all days, at least p < 0.001) throughout postnatal life. While both cohorts displayed a similar trend with an initial increase with a Scr peak on Days 3 and 4 and a subsequent decrease, the difference in within-day median values fluctuated between 11 and 24 mmol.L(-1). There is neither fixed nor relative difference in Scr between both techniques.
  
  
  CONCLUSIONS
  When using Scr to estimate renal function in ELBW neonates, clinicians should in addition to the postnatal changes and other covariates of renal function, also consider the technique applied. We provide reference values and comparison between both techniques.
authors.affiliation: Neonatal Intensive Care Unit, University Hospitals Leuven, Leuven, Belgium. karel.allegaert@uz.kuleuven.ac.be
authors.forename: Karel
authors.initials: K
authors.lastname: Allegaert
authors.forename: Maike
authors.initials: M
authors.lastname: Kuppens
authors.forename: Djalila
authors.initials: D
authors.lastname: Mekahli
authors.forename: Elena
authors.initials: E
authors.lastname: Levtchenko
authors.forename: Florent
authors.initials: F
authors.lastname: Vanstapel
authors.forename: Christine
authors.initials: C
authors.lastname: Vanhole
authors.forename: John N
authors.initials: JN
authors.lastname: van den Anker
mesh_terms: D015415:Biomarkers / Q000032:analysis / Q000097:blood; D015331:Cohort Studies; D003124:Colorimetry / Q000379:methods / Q000592:standards; D003404:Creatinine / Q000032:analysis / Q000097:blood / Q000592:standards*; D057075:Enzyme Assays / Q000379:methods / Q000592:standards; D005260:Female; D005919:Glomerular Filtration Rate / Q000502:physiology; D006801:Humans; D052577:Infant, Extremely Low Birth Weight / Q000097:blood*; D007231:Infant, Newborn; D007677:Kidney Function Tests / Q000379:methods* / Q000592:standards*; D008297:Male; D015997:Neonatal Screening / Q000379:methods / Q000592:standards; D012016:Reference Values
chemical_list: D015415:Biomarkers; D003404:Creatinine