title: A new approach to CD34+ hematopoietic progenitor cell counting.
abstract: BACKGROUND
  In the absence of a gold standard for hematopoietic progenitor counting, the intra-laboratory variation between commonly used strategies for progenitor assessment was compared.
  
  
  METHODS
  We used a pool of FITC-conjugated monoclonal antibodies (CD14, CD11b) and PE-CD34 to facilitate CD34 counting, excluding CD14(+)/CD11b(+) bright cells. We compared this protocol with other common methodologies, such as the single-staining approach, known as the Milan method, and the ISHAGE multiparameter method.
  
  
  RESULTS
  We show that the CD14/CD11b protocol is a valid approach to progenitor cell counting. Though different methods give different results for progenitor cell counting, Lin's coefficient shows high concordance among flow cytometry counts but a substantial difference with colony- forming unit counts. Both the ISHAGE and CD14/CD11b protocol give higher counts than the Milan method. Moreover, on revising the ISHAGE analysis, we described a rare population of cells with the CD34(+)CD45(neg) phenotype, which could have an impact in CD34 counting.
  
  
  CONCLUSIONS
  We have designed a valid alternative approach for hematopoietic progenitor cell counting, and we show that different methods give different results.
authors.affiliation: Servei d'Hemoteràpia i Hemostàsia, Hospital Clínic, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Universitat de Barcelona, Barcelona, Spain.
authors.forename: Pedro
authors.initials: P
authors.lastname: Marín
authors.forename: Lluís
authors.initials: L
authors.lastname: Jover
authors.forename: Jordi
authors.initials: J
authors.lastname: Petriz
mesh_terms: D018952:Antigens, CD34 / Q000378:metabolism*; D002452:Cell Count / Q000379:methods*; D003114:Colony-Forming Units Assay; D005434:Flow Cytometry; D006412:Hematopoietic Stem Cells / Q000166:cytology*; D006801:Humans; D017493:Leukocyte Common Antigens / Q000378:metabolism; D015203:Reproducibility of Results
chemical_list: D018952:Antigens, CD34; D017493:Leukocyte Common Antigens