title: Flow cytometric determination of residual white blood cell levels in preserved samples from leukoreduced blood products.
abstract: BACKGROUND
  In preparation for a proposed consolidated testing service, Canadian Blood Services undertook the evaluation of a commercial test kit for the enumeration by flow cytometry of residual white blood cells (rWBCs) present in preserved samples recovered from leukoreduced (LR) blood and platelet products.
  
  
  METHODS
  The stability of preserved WBCs, the equivalency of WBCs used for spiking, test method precision, specificity, reliability, accuracy, and sensitivity were investigated. For comparative purposes, WBC counts were also determined by Nageotte as well as by flow cytometry.
  
  
  RESULTS
  WBCs were stable up to 4 weeks at room temperature for all components by either method. Within methods, no differences were observed due to the source of WBC used for spiking purposes. By either method, test precision was acceptable (<20% coefficient of variation) and of similar reliability at a target value of 10 +/- 5 WBCs per microL. The flow cytometric method was shown to be more specific and accurate than the Nageotte method. Sensitivity by either method was 0.1 WBCs per microL. On average, Nageotte counts were lower than those observed by flow cytometry.
  
  
  CONCLUSIONS
  These results demonstrate that WBCs in WBC stabilizing solution-treated samples from LR blood components were stabilized up to 4 weeks at room temperature and that rWBC determinations made with a WBC enumeration kit by flow cytometry have the required precision, specificity, reliability, and accuracy in the relevant test range. This validated WBC stabilization and flow cytometric counting method is considered acceptable as part of a quality control program for leukoreduced blood products.
authors: Canadian Blood Services, National Testing Laboratory, Ottawa, Ontario, Canada. doug.palmer@blood.ca
authors: Douglas S
authors: DS
authors: Palmer
authors: Paul
authors: P
authors: Birch
authors: Joan
authors: J
authors: O'Toole
authors: Deborah
authors: D
authors: Henderson
authors: Vito
authors: V
authors: Scalia
mesh_terms: D000094902:Blood Banking / Q000379:methods; D001793:Blood Preservation / Q000592:standards*; D002170:Canada; D005434:Flow Cytometry / Q000592:standards*; D006801:Humans; D007958:Leukocyte Count; D047589:Leukocyte Reduction Procedures; D007962:Leukocytes; D011786:Quality Control; D013696:Temperature; D013997:Time Factors