title: Reducing costs in flow-cytometric counting of residual white blood cells in blood products: utilization of a single-platform bead-free flow-rate calibration method.
abstract: BACKGROUND
  Commercial flow-cytometric methods for counting residual white blood cells (rWBCs) in leukoreduced blood products use calibration beads for estimation of the measured sample volume. A bead-free flow-rate calibration method is developed and validated.
  
  
  METHODS
  The analyzed volume was calculated by acquisition time (ACQ). Twenty-nine spiking series of red blood cell (RBC) or platelet (PLT) products were prepared containing levels ranging from 0.08 × 10(6) up to 2048 × 10(6) WBCs/L. Nearly WBC-free triple-leukofiltered RBCs or PLT concentrates (PCs) served as background. Propidium iodide (PI) was used to identify rWBCs. Five RBC series were compared against a commercially available kit (LeukoSure, Beckman Coulter). Routine capabilities were tested on 41 RBC and 92 PC samples of two independent transfusion services.
  
  
  RESULTS
  The lower detection limit in RBC was 0.08 × 10(6) rWBCs/L for ACQ and 0.16 for LeukoSure. Criteria for linearity, accuracy, and precision were fulfilled within the range of 0.5 × 10(6) to 512 × 10(6) WBCs/L. For PCs, all these criteria were fulfilled between 0.5 × 10(6) and 32 × 10(6) rWBCs/L (lower detection limit of 0.25) for PI. ACQ and LeukoSure agreed sufficiently (81%) when tested on routine RBCs or PCs.
  
  
  CONCLUSIONS
  A residual WBC count of fewer than 0.5 × 10(6) WBCs/L can be accurately counted using the ACQ approach at a total reagent cost of less than 0.5€ per sample.
authors.affiliation: Institute for Transplantation Diagnostics and Cell Therapy, University of Duesseldorf, Duesseldorf, Germany. fischer@itz.uni-duesseldorf.de
authors.forename: Johannes C
authors.initials: JC
authors.lastname: Fischer
authors.forename: Ernst M
authors.initials: EM
authors.lastname: Quenzel
authors.forename: Rainer
authors.initials: R
authors.lastname: Moog
authors.forename: Folker
authors.initials: F
authors.lastname: Wenzel
authors.forename: Regina
authors.initials: R
authors.lastname: Riethmacher
authors.forename: Boris
authors.initials: B
authors.lastname: Tutschek
authors.forename: Günther
authors.initials: G
authors.lastname: Giers
mesh_terms: D002138:Calibration; D003365:Costs and Cost Analysis; D017707:Erythrocyte Transfusion / Q000592:standards; D005434:Flow Cytometry / Q000191:economics / Q000379:methods*; D006801:Humans; D007958:Leukocyte Count / Q000191:economics* / Q000295:instrumentation / Q000379:methods*; D047589:Leukocyte Reduction Procedures / Q000379:methods*; D057230:Limit of Detection; D010983:Plateletpheresis / Q000592:standards; D011786:Quality Control