title: New rapid flow cytometric method for the enumeration of nucleated red blood cells.
abstract: BACKGROUND
  Nucleated red blood cells (NRBC) in blood specimens compromise the automated white blood cell (WBC) count on most hematology analyzers. This makes it necessary to correct the WBC count by subtracting separately counted NRBC by manual microscopy. In addition, it is clinically important to establish the non-physiological presence of NRBC in blood specimens because of their association with significant hematological and non-hematological disease. Unfortunately, manual microscopic methods lack sensitivity, specificity and reproducibility required for both.
  
  
  METHODS
  We have developed a new, rapid flow cytometric method for the detection and enumeration of NRBC, based on two-color staining with anti-CD45-fluorescein-isothiocyanate (CD45-FITC) and propidium iodide (PI). EDTA anticoagulated blood samples are incubated for 30 min with CD45-FITC, followed by 30 sec acid-hypotonic lysis, containing PI and subsequent addition of an alkaline-hypertonic solution. The samples are thus ready for flow cytometric analysis.
  
  
  RESULTS
  The method typically yields up to four populations, (1) red blood cell (RBC) ghosts, debris, lyse-resistant RBC, reticulocytes and platelets, (2) CD45(+) WBC unstained by PI, (3) CD45(+) WBC stained by PI, and (4) CD45(-)/PI(bright) NRBC. Manual microscopic reference NRBC counts of 25 patient specimens showed excellent correlation with flow cytometric NRBC determinations (y = 0.943x+0. 66; r(2) = 0.982). Performance for precision showed a mean coefficient of variation (CV) for the flow cytometric method of =10%, with a mean CV for manual NRBC counts of 40%.
  
  
  CONCLUSIONS
  We conclude that this method is suitable for NRBC counting in peripheral blood specimens with improved performance in terms of accuracy, reproducibility when compared to manual microscopic methods.
authors.affiliation: Reagent Development Group, Sysmex Corporation, Kobe, Japan. tsuji@ini.sysmex.co.jp
authors.forename: T
authors.initials: T
authors.lastname: Tsuji
authors.forename: T
authors.initials: T
authors.lastname: Sakata
authors.forename: Y
authors.initials: Y
authors.lastname: Hamaguchi
authors.forename: F s
authors.initials: Fs
authors.lastname: Wang
authors.forename: B
authors.initials: B
authors.lastname: Houwen
mesh_terms: D000328:Adult; D001793:Blood Preservation; D004900:Erythroblasts / Q000166:cytology*; D004906:Erythrocyte Count / Q000379:methods*; D005434:Flow Cytometry / Q000379:methods* / Q000592:standards; D016650:Fluorescein-5-isothiocyanate; D005456:Fluorescent Dyes; D006801:Humans; D017493:Leukocyte Common Antigens; D010974:Platelet Aggregation; D015203:Reproducibility of Results
chemical_list: D005456:Fluorescent Dyes; D017493:Leukocyte Common Antigens; D016650:Fluorescein-5-isothiocyanate