title: Interchangeability of measurements of CA 19-9 in serum with four frequently used assays: an update.
abstract: BACKGROUND
  CA 19-9 is a marker principally related to pancreatic and gall bladder cancer. Although its determination has no value in screening for these malignancies, it is used in post-operative monitoring and during chemotherapeutic treatment of confirmed disease. Measurements during follow-up must be comparable and must be performed with standard, validated methods.
  
  
  METHODS
  We compared four routinely used analytical systems for CA 19-9 determination: the Architect i2000 and AxSYM systems from Abbott Laboratories, the Elecsys 1010 from Roche Diagnostics, and the KRYPTOR system from Brahms Diagnostics. We evaluated the analytical performance of the four systems and compared measurements of CA 19-9 values, which covered the whole analytical range.
  
  
  RESULTS
  The analytical performance and accuracy of the four systems were fairly good, but Passing-Bablok regression and mountain plots showed significant differences in CA 19-9 values measured with the four platforms.
  
  
  CONCLUSIONS
  Our data indicate that during tumor follow-up, the use of the same system is appropriate to avoid the risk of a variation due to the method rather than the disease. Moreover, whenever a change in analytical equipment is required, careful analysis of CA 19-9 results must be undertaken.
authors.affiliation: Laboratory Medicine Unit, European Institute of Oncology, Milan, Italy. rita.passerini@ieo.it
authors.forename: Rita
authors.initials: R
authors.lastname: Passerini
authors.forename: Daniela
authors.initials: D
authors.lastname: Riggio
authors.forename: Michela
authors.initials: M
authors.lastname: Salvatici
authors.forename: Laura
authors.initials: L
authors.lastname: Zorzino
authors.forename: Davide
authors.initials: D
authors.lastname: Radice
authors.forename: Maria Teresa
authors.initials: MT
authors.lastname: Sandri
mesh_terms: D001681:Biological Assay; D018395:CA-19-9 Antigen / Q000097:blood* / Q000276:immunology; D006801:Humans; D007124:Immunoenzyme Techniques / Q000379:methods* / Q000592:standards; D009369:Neoplasms / Q000097:blood* / Q000276:immunology / Q000628:therapy; D011933:Reagent Kits, Diagnostic / Q000592:standards; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D018395:CA-19-9 Antigen; D011933:Reagent Kits, Diagnostic