Quality control study of the Italian group of cytometry on flow cytometry DNA content measurements: II. Factors affecting inter- and intralaboratory variability

D. Tirindelli Danesi, M. Spanò, P. Altavista, M. Pantarotto, C. Filippini, G. Mazzini, E. Erba, P. Ubezio

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Abstract

A multicentric national quality control study has been organized under the auspices of the Italian Group of Cytometry to find a possible influence of some procedural steps in DNA flow cytometry measurements on DNA index (DI) values and to identity the main parameters affecting the interlaboratory variability. To 40 participating laboratories we provided suspensions containing unknown mixtures of different cell types: an homogeneous thymocyte population used to check instrument linearity; one mixture composed of two cell types characterized by DI = 1.00 and 1.10; and another composed of three different cell types with relative DIs of 1.00, 1.26, and 1.62, respectively. Possible effects due to staining protocols were studied, allowing the participants to stain cellular DNA according to the procedure routinely adopted in each laboratory, in addition to a standardized procedure with a fixed PI solution. As far as the influence of instrument linearity on DI values is concerned, we did not find any correlation with the DI variability observed, even if the use of a standardized staining protocol could lead to a sensible gain in interlaboratory DI reproducibility. Twenty-five of 40 (65%) laboratories were able to discriminate the near-diploid subpopulation, and a coefficient of variation of less than 4% was the minimum condition necessary to recognize the DI = 1.1 population. In samples containing two aneuploid subpopulations, 25 of 35 (71.4%) laboratories showed a high reproducibility with the standard staining protocol and 22 of 38 (57.9%) with the free staining protocol. However, a sensible improvement in interlaboratory reproducibility emerged with respect to the previous trial (Tirindelli Danesi et al.: Cytometry 14:576-583, 1993).
Original languageEnglish
Pages (from-to)85 - 97
Number of pages13
JournalCytometry
Volume30
Issue number2
DOIs
Publication statusPublished - 15 Apr 1997
Externally publishedYes

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All Science Journal Classification (ASJC) codes

  • Pathology and Forensic Medicine
  • Biophysics
  • Hematology
  • Endocrinology
  • Cell Biology

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