title: Basal levels of CD34 positive cells in peripheral blood differ between individuals and are stable for 18 months.
abstract: BACKGROUND
  Detection of basal levels of CD34 progenitor cells is a rare event analysis enumerating cells down to 1 cell/μl. A reproducible analytic approach was used in three independent clinical trials in which multiple sequential assays were obtained from the same individual.
  
  
  METHODS
  A 4 color panel combining, HLA-DR, CD34, CD45, and CD11b was used in a dual platform analysis to quantify CD34 progenitor cells in peripheral blood, with quality control focused at the lowest measurements (i.e., basal levels), where assay error is greatest.
  
  
  RESULTS
  Repeat testing of individuals every 4 h over the course of 6 days provided a unique opportunity to assess the precision of the analytic technique and identified basal differences between individuals. In a second study, the basal levels were stable for 10 weeks while in a third study the individual differences were maintained for 18 months. This approach was then used to monitor the kinetics of mobilization of CD34 cells following G-CSF stimulation every 4 h.
  
  
  CONCLUSIONS
  The differences between individuals in basal levels of CD34 were shown to be a biologic constant, stable for 18 months and not a result of the variability of the assay, shown by low coefficients of variation for each individual. These results can be used to augment a quality control program by monitoring individuals over time to establish intra and inter-laboratory assay precision. In addition, the response of six individuals to G-CSF demonstrated differences in absolute numbers of mobilized CD34 progenitor cells but showed identical kinetics, peaking at 80-110 h.
authors.affiliation: Hematologics, Inc., Seattle, Washington, USA. lisa@hematologics.com
authors.forename: Lisa
authors.initials: L
authors.lastname: Eidenschink
authors.forename: Gere
authors.initials: G
authors.lastname: DiZerega
authors.forename: Kathy
authors.initials: K
authors.lastname: Rodgers
authors.forename: Mark
authors.initials: M
authors.lastname: Bartlett
authors.forename: Denise A
authors.initials: DA
authors.lastname: Wells
authors.forename: Michael R
authors.initials: MR
authors.lastname: Loken
mesh_terms: D000293:Adolescent; D000328:Adult; D018952:Antigens, CD34 / Q000378:metabolism*; D001772:Blood Cell Count; D001793:Blood Preservation; D002452:Cell Count; D005260:Female; D014644:Genetic Variation; D016179:Granulocyte Colony-Stimulating Factor / Q000494:pharmacology*; D019650:Hematopoietic Stem Cell Mobilization / Q000379:methods; D006412:Hematopoietic Stem Cells / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D013997:Time Factors; D055815:Young Adult
chemical_list: D018952:Antigens, CD34; D016179:Granulocyte Colony-Stimulating Factor