title: Application of five frozen human-pooled serum samples assigned by the International Federation of Clinical Chemistry and Laboratory Medicine reference procedure in a traceability investigation of gamma-glutamyltransferase catalytic concentration measurements in China.
abstract: BACKGROUND
  The in vitro directive of the European Union requires traceability to the international recommended reference procedures. The application of the reference procedures is necessary in order to evaluate the accuracy of gamma-glutamyltransferase (GGT) assays of routine measurement systems in China.
  
  
  METHODS
  Five frozen patient-pooled serum samples were assigned values by the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) reference procedure in order to evaluate the traceability of the results of GGT catalytic activity from six homogeneous systems. One of the serum samples was used to calibrate seven non-homogeneous systems.
  
  
  RESULTS
  All of the homogeneous systems, except the Dade system (Dade Bering Inc, IL, USA), achieved traceability within the measurement range. The Roche and Hitachi systems were better than the other systems. After calibration, the variance of the non-homogeneous systems decreased dramatically from between 14.50% and 25.23% to between 1.25% and 3.09% and the bias decreased from between -11.4% and -4.1% to between 0.5% and 3.5%.
  
  
  CONCLUSIONS
  Manufacturers in China should ensure that their calibration systems correspond to the IFCC reference procedures. Fresh frozen pooled patient serum assigned by reference laboratories can be used to calibrate non-homogeneous systems in order to achieve traceability.
authors.affiliation: Clinical Laboratory Department, Peking University First Hospital, Beijing, China.
authors.forename: Changyu
authors.initials: C
authors.lastname: Xia
authors.forename: Qing
authors.initials: Q
authors.lastname: Tong
authors.forename: Qingtao
authors.initials: Q
authors.lastname: Wang
authors.forename: Zhuling
authors.initials: Z
authors.lastname: Tang
authors.forename: Lili
authors.initials: L
authors.lastname: Qi
authors.forename: Shan
authors.initials: S
authors.lastname: Chi
authors.forename: Man
authors.initials: M
authors.lastname: Zhang
authors.forename: Xuejing
authors.initials: X
authors.lastname: Wang
authors.forename: Haixia
authors.initials: H
authors.lastname: Li
authors.forename: Guobin
authors.initials: G
authors.lastname: Xu
mesh_terms: D002138:Calibration; D002681:China; D004796:Clinical Enzyme Tests / Q000592:standards*; D017408:Guidelines as Topic; D006801:Humans; D011786:Quality Control; D012015:Reference Standards; D005723:gamma-Glutamyltransferase / Q000032:analysis / Q000592:standards*
chemical_list: D005723:gamma-Glutamyltransferase