title: Improved DNA flow cytometric, DNA ploidy, and S-phase reproducibility between 15 laboratories in analysis of breast cancer using generalized guidelines.
abstract: BACKGROUND
  Lack of generalized guidelines for DNA flow cytometric analysis (FCM) may be the main reason for its limited use in the clinical management of breast cancer.
  
  
  METHODS
  After an initial interlaboratory reproducibility study (Round I), we concluded that it was the evaluation of the DNA histograms rather than the technical performance of the analysis that was the main reason for discordant results between laboratories. Guidelines for the interpretation of DNA histograms were therefore drawn up. We present here data from a new reproducibility study (Round II) using these guidelines.
  
  
  RESULTS
  For 10 laboratories also participating in Round I, use of the guidelines increased the concordance in DNA ploidy status from 89% to 100% for the 46 samples used in both rounds. The concordance rate for SPF also increased; mean r(s)-value increased from 0.81 to 0.88, and mean kappa value (lower two-thirds versus upper third versus not reported) increased from 0.55 to 0.71. Five new laboratories, participating only in Round II, also agreed with the 10 original laboratories regarding DNA ploidy status. With the inclusion of all 15 laboratories, we obtained a mean r(s)-value of 0.81 and a mean kappa value of 0.72 for SPF.
  
  
  CONCLUSIONS
  Generalized guidelines for DNA FCM increase interlaboratory agreement, which is highly important in clinical routines and in multicenter studies. Furthermore, inexperienced FCM laboratories using generalized guidelines can produce and interpret DNA FCM data equally as well as experienced laboratories.
authors.affiliation: Department of Oncology, University Hospital, SE-221 85 Lund, Sweden. bo.baldetorp@onk.lu.se
authors.forename: Bo
authors.initials: B
authors.lastname: Baldetorp
authors.forename: Pär-Ola
authors.initials: PO
authors.lastname: Bendahl
authors.forename: Mårten
authors.initials: M
authors.lastname: Fernö
authors.forename: Olle
authors.initials: O
authors.lastname: Stål
mesh_terms: D001943:Breast Neoplasms / Q000235:genetics*; D002467:Cell Nucleus / Q000378:metabolism; D004247:DNA / Q000032:analysis* / Q000737:chemistry; D004171:Diploidy; D005434:Flow Cytometry / Q000379:methods*; D017408:Guidelines as Topic; D006801:Humans; D011003:Ploidies; D015203:Reproducibility of Results; D016196:S Phase
chemical_list: D004247:DNA