title: European proficiency study with control serum for the tumor marker CA 19-9 measured on different test systems.
abstract: BACKGROUND
  Reliable and precise CA 19-9 testing is required for the long-term follow-up of patients with pancreatic carcinoma during therapy. The aim of this longitudinal proficiency study was to evaluate the comparability, linearity, and precision of CA 19-9 determinations performed in different laboratories using currently available test systems under routine conditions.
  
  
  METHODS
  During the one year study period, 15 laboratories applied 7 different tests and included a liquid BIOREF control serum with pancreatic carcinoma derived CA 19-9 in their routine testing and quality control procedures. The results were collected centrally and evaluated statistically.
  
  
  RESULTS
  The comparability of CA 19-9 results is limited especially when different tests are used, albeit, some tests show a good correlation: The CA 19-9 values obtained by different laboratories using different test systems vary up to a factor of 2. The precision of CA 19-9 determinations was acceptable in most laboratories with coefficients of variation ranging between very low 3.2% and high 17.8%. The imprecision was slightly increased when automatic dilution procedures of the analysers were used.
  
  
  CONCLUSIONS
  The comparability of CA 19-9 test results must be improved. The precision is acceptable in most cases. In order to monitor key performance parameters, every laboratory should participate in external quality assessment schemes and should perform a routine internal quality control with a control serum independent from the test kit manufacturer.
authors.affiliation: Klinikum Nürnberg, Institut für Klinische Chemie, Labormedizin und Transfusionsmedizin, Nürnberg, Germany. thomas.bertsch@klinikum-nuernberg.de
authors.forename: T
authors.initials: T
authors.lastname: Bertsch
authors.forename: C
authors.initials: C
authors.lastname: Aschenneller
authors.forename: N
authors.initials: N
authors.lastname: Bewarder
authors.forename: R
authors.initials: R
authors.lastname: Beyrau
authors.forename: B L
authors.initials: BL
authors.lastname: Herrmann
authors.forename: E
authors.initials: E
authors.lastname: Jansen
authors.forename: R
authors.initials: R
authors.lastname: Klapdor
authors.forename: M
authors.initials: M
authors.lastname: Klemm
authors.forename: J
authors.initials: J
authors.lastname: Meissner
authors.forename: S
authors.initials: S
authors.lastname: Pfeiffer
authors.forename: I
authors.initials: I
authors.lastname: Schauer
authors.forename: M M
authors.initials: MM
authors.lastname: Stratmann
authors.forename: C
authors.initials: C
authors.lastname: Theimer
authors.forename: H M
authors.initials: HM
authors.lastname: van de Loo
authors.forename: D A
authors.initials: DA
authors.lastname: Wildbredt
authors.forename: C
authors.initials: C
authors.lastname: Wolff
authors.forename: P
authors.initials: P
authors.lastname: Wollenberg
mesh_terms: D014408:Biomarkers, Tumor / Q000097:blood*; D018395:CA-19-9 Antigen / Q000097:blood*; D006801:Humans; D008137:Longitudinal Studies; D010190:Pancreatic Neoplasms / Q000097:blood*; D011786:Quality Control; D015203:Reproducibility of Results
chemical_list: D014408:Biomarkers, Tumor; D018395:CA-19-9 Antigen