title: Correction of pseudoreticulocytosis in leukocytosis samples using the Sysmex XE-2100 analyzer depends on the type and number of white blood cells.
abstract: BACKGROUND
  The reticulocyte count is a good marker of erythropoietic activity of the bone marrow. In the mid-1990s, automated flow cytometric analysis replaced microscopy for the quantification of reticulocytes. Leukocytosis cases with an erroneously high reticulocyte count and a high immature reticulocyte fraction (IRF) have been reported. In this study, we analyzed reticulocyte counts in leukocytosis samples, in an effort to identify a correction method.
  
  
  METHODS
  The study comprised of 21 samples from 16 leukocytosis patients. Results of reticulocyte analyses obtained using a XE-2100 hematology analyzer (Sysmex, Japan) were compared with those obtained using the supravital staining technique, which is a reference method. If the samples showed erroneously high reticulocyte counts and IRF, they were reanalyzed after serial dilution with isotonic solution.
  
  
  RESULTS
  Five samples from 4 patients showed erroneously elevated reticulocyte counts and/or IRF on the XE-2100 analyzer. They displayed abnormal reticulocyte scattergrams, with 4 of 5 cases indicated by a flag. The white blood cell (WBC) fractions overlapped with the reticulocyte regions, especially with the IRF. Diagnoses and blast counts were variable when such errors occurred; WBC counts varied from 218.19×10(9)/L to 725.14×10(9)/L. The errors were corrected by simple dilution with isotonic solution. However, the corrective WBC counts differed according to individual cases.
  
  
  CONCLUSIONS
  When leukocytosis samples exhibit an abnormal reticulocyte scattergram with a flag, or an abnormally high IRF, we recommend the dilution of the sample with isotonic solution to a WBC count of about 100.00×10(9)/L, followed by reanalysis of the reticulocyte count and reticulocyte scattergram.
authors.affiliation: Department of Laboratory Medicine, The Catholic University of Korea College of Medicine, Seoul, Korea.
authors.forename: Ahhyun
authors.initials: A
authors.lastname: Kim
authors.forename: Joonhong
authors.initials: J
authors.lastname: Park
authors.forename: Myungshin
authors.initials: M
authors.lastname: Kim
authors.forename: Jihyang
authors.initials: J
authors.lastname: Lim
authors.forename: Eun-Jee
authors.initials: EJ
authors.lastname: Oh
authors.forename: Yonggoo
authors.initials: Y
authors.lastname: Kim
authors.forename: Yeon-Joon
authors.initials: YJ
authors.lastname: Park
authors.forename: Kyungja
authors.initials: K
authors.lastname: Han
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001331:Automation; D002675:Child, Preschool; D005260:Female; D005434:Flow Cytometry / Q000295:instrumentation / Q000379:methods*; D006801:Humans; D007201:Indicator Dilution Techniques; D007231:Infant, Newborn; D007958:Leukocyte Count; D007962:Leukocytes / Q000166:cytology; D007964:Leukocytosis / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D017701:Reticulocyte Count; D012156:Reticulocytes / Q000166:cytology; D055815:Young Adult
keywords: Leukocytosis; Reticulocyte count; Reticulocytes