title: Clinical utility of the absolute number of circulating CD34-positive cells in patients with chronic myeloproliferative disorders.
abstract: OBJECTIVE
  Flow cytometry enumeration of peripheral blood CD34-positive cells provides reliable measurements of circulating hematopoietic progenitors in humans. Since the absolute number of circulating CD34-positive cells has been previously found to be elevated in myelofibrosis with myeloid metaplasia (MMM), we prospectively studied the clinical utility of this parameter in the work-up of patients with chronic myeloproliferative disorders.
  
  
  METHODS
  Of the 248 consecutive patients enrolled in this study, 106 had polycythemia vera (PV), 90 essential thrombocythemia (ET), and 52 myelofibrosis with myeloid metaplasia (MMM). The study population included both newly diagnosed and established cases, and of these latter some patients were on cytoreductive treatment while others were chemotherapy naive. Both cross-sectional and longitudinal investigations were carried out. Flow cytometry enumeration of CD34-positive cells was performed using a single-platform assay.
  
  
  RESULTS
  Median numbers and ranges of circulating CD34-positive cells were 2.3x10(6)/L (0-5) in 20 control subjects, 2.2x10(6)/L (0-14) in those with PV, 2.4x10(6)/L (0-14) in those with ET, and 114x10(6)/L (6-2,520) in MMM patients. Analysis of variance demonstrated that values were markedly higher in MMM patients than in the remaining groups, and counts did not appear to fluctuate over short periods of follow-up. In both cross-sectional and longitudinal investigations on patients at clinical onset and/or out of cytoreductive treatment, a CD34-positive count of > or = 15x10(6)/L was always associated with MMM, clearly indicating a disease-related specificity.
  
  
  CONCLUSIONS
  The absolute number of circulating CD34-positive cells is normal or anyhow lower than 15x10(6)/L in patients with uncomplicated PV or ET, whereas it is equal or above this cut-off in those with MMM, likely reflecting abnormal hematopoietic progenitor cell trafficking. Thus, enumeration of circulating CD34-positive cells may be useful in the work-up of patients with myeloproliferative disorders.
authors.affiliation: Division of Hematology, University of Pavia Medical School & IRCCS Policlinico S. Matteo, Pavia, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Passamonti
authors.forename: Laura
authors.initials: L
authors.lastname: Vanelli
authors.forename: Lucia
authors.initials: L
authors.lastname: Malabarba
authors.forename: Elisa
authors.initials: E
authors.lastname: Rumi
authors.forename: Ester
authors.initials: E
authors.lastname: Pungolino
authors.forename: Luca
authors.initials: L
authors.lastname: Malcovati
authors.forename: Cristiana
authors.initials: C
authors.lastname: Pascutto
authors.forename: Enrica
authors.initials: E
authors.lastname: Morra
authors.forename: Mario
authors.initials: M
authors.lastname: Lazzarino
authors.forename: Mario
authors.initials: M
authors.lastname: Cazzola
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D018952:Antigens, CD34 / Q000097:blood* / Q000378:metabolism*; D015415:Biomarkers / Q000097:blood; D002452:Cell Count; D003430:Cross-Sectional Studies; D005260:Female; D006412:Hematopoietic Stem Cells / Q000378:metabolism*; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009196:Myeloproliferative Disorders / Q000097:blood*; D011087:Polycythemia Vera / Q000097:blood; D055728:Primary Myelofibrosis / Q000097:blood; D011446:Prospective Studies; D013920:Thrombocythemia, Essential / Q000097:blood
chemical_list: D018952:Antigens, CD34; D015415:Biomarkers