title: Crossover study of three methods for low-level white blood cell counting on two types of flow cytometer.
abstract: BACKGROUND
  Flow cytometric methods were previously shown to be preferable to microscopic and volumetric methods for counting residual white blood cells (WBCs). In this study, three flow cytometric, low-level WBC counting methods were cross compared using two flow cytometers.
  
  
  METHODS
  Double-filtered red cell and platelet concentrates were spiked with different amounts of WBC to obtain panels of unspiked and 0.3, 1.0, 3.3, and 10.0 WBC/microl. The methods of BD Biosciences (BDB), Beckman-Coulter (BC), and an in-house method were performed on flow cytometers from BDB and BC. Samples were measured in ninefold. We required that (a) r(2) be at least 0.98 (linearity), (b) at least 80% of observations fell within 20% of expected values (accuracy), and (c) the coefficients of variation be at least 20% (precision) for samples containing at least 3.3 WBC/microl.
  
  
  RESULTS
  For the red cell panel, our requirements were met by the BDB method on both flow cytometers and by the BC and in-house methods on the BDB flow cytometer only. For the platelet panel, our requirements were met on all combinations of methods and flow cytometers, except for the in-house method on the BDB flow cytometer. Intra-assay variation was lowest for the BDB method, irrespective of the type of flow cytometer used.
  
  
  CONCLUSIONS
  Based on accuracy and precision, the BDB method on the BDB flow cytometer produced the best results for counting low-level WBCs.
authors.affiliation: Sanquin Working Party for Low Level Leukocyte Counting, Amsterdam, The Netherlands. m.dijkstra@sanquin.nl
authors.forename: M J
authors.initials: MJ
authors.lastname: Dijkstra-Tiekstra
authors.forename: J G
authors.initials: JG
authors.lastname: Schrijver
authors.forename: P F
authors.initials: PF
authors.lastname: van der Meer
authors.forename: R F
authors.initials: RF
authors.lastname: Laport
authors.forename: J W
authors.initials: JW
authors.lastname: Gratama
authors.forename: W H B M
authors.initials: WH
authors.lastname: Levering
authors.forename: C J
authors.initials: CJ
authors.lastname: van Delden
authors.forename: J
authors.initials: J
authors.lastname: de Wildt-Eggen
mesh_terms: D002469:Cell Separation; D018592:Cross-Over Studies; D005434:Flow Cytometry / Q000295:instrumentation* / Q000379:methods*; D006801:Humans; D007958:Leukocyte Count / Q000295:instrumentation* / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity