title: Traceability of values for catalytic activity concentration of enzymes: a Certified Reference Material for aspartate transaminase.
abstract: BACKGROUND
  A new reference material for the liver enzyme aspartate transaminase (AST) (L-aspartate: 2-oxoglutarate-aminotransferase, EC 2.6.1.1), also called aspartate aminotransferase (ASAT), has been developed under the code ERM-AD457/IFCC. This certified reference material (CRM) for AST has been produced from a human type recombinant AST expressed in Escherichia coli and a buffer containing bovine serum albumin, and has been lyophilised.
  
  
  METHODS
  The homogeneity and the stability of the material have been tested and the catalytic activity concentration has been characterised by 12 laboratories using the reference procedure for AST at 37 degrees C from the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC).
  
  
  RESULTS
  The certified catalytic activity concentration and certified uncertainty of AST in the reconstituted material are (1.74+/-0.05) microkat/L or (104.6+/-2.7) U/L (with a coverage factor k=2; 95% confidence interval).
  
  
  CONCLUSIONS
  Both the certified value and uncertainty are traceable to the International System of Units (SI). The material is aiming to control the IFCC reference procedure for AST at 37 degrees C, which will then be used to assign values to calibrants and control materials. The present paper highlights the scientific challenges and innovations which were encountered during the development of this new CRM.
authors.affiliation: Institute for Reference Materials and Measurements (IRMM), Joint Research Centre, European Commission, Geel, Belgium. Brigitte.Toussaint@ec.europa.eu
authors.forename: Brigitte
authors.initials: B
authors.lastname: Toussaint
authors.forename: Hendrik
authors.initials: H
authors.lastname: Emons
authors.forename: Heinz G
authors.initials: HG
authors.lastname: Schimmel
authors.forename: Steffen
authors.initials: S
authors.lastname: Bossert-Reuther
authors.forename: Francesca
authors.initials: F
authors.lastname: Canalias
authors.forename: Ferruccio
authors.initials: F
authors.lastname: Ceriotti
authors.forename: Georges
authors.initials: G
authors.lastname: Férard
authors.forename: Carlo A
authors.initials: CA
authors.lastname: Ferrero
authors.forename: Paul F H
authors.initials: PF
authors.lastname: Franck
authors.forename: F Javier
authors.initials: FJ
authors.lastname: Gella
authors.forename: Joseph
authors.initials: J
authors.lastname: Henny
authors.forename: Poul J
authors.initials: PJ
authors.lastname: Jørgensen
authors.forename: Rainer
authors.initials: R
authors.lastname: Klauke
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Lessinger
authors.forename: Daniel
authors.initials: D
authors.lastname: Mazziotta
authors.forename: Mauro
authors.initials: M
authors.lastname: Panteghini
authors.forename: Shigeru
authors.initials: S
authors.lastname: Ueda
authors.forename: Gerhard
authors.initials: G
authors.lastname: Schumann
mesh_terms: D000818:Animals; D001219:Aspartate Aminotransferases / Q000032:analysis / Q000235:genetics / Q000592:standards*; D002417:Cattle; D004796:Clinical Enzyme Tests / Q000379:methods / Q000592:standards*; D006801:Humans; D011994:Recombinant Proteins / Q000032:analysis / Q000235:genetics / Q000592:standards; D012015:Reference Standards; D012710:Serum Albumin, Bovine / Q000737:chemistry; D035501:Uncertainty
chemical_list: D011994:Recombinant Proteins; D012710:Serum Albumin, Bovine; D001219:Aspartate Aminotransferases