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Ann Lab Med. 2012 November; 32(6): 392–398.
Published online 2012 October 17. doi:  10.3343/alm.2012.32.6.392
PMCID: PMC3486932

Correction of Pseudoreticulocytosis in Leukocytosis Samples Using the Sysmex XE-2100 Analyzer Depends on the Type and Number of White Blood Cells

Ahhyun Kim, M.D., Joonhong Park, M.D., Myungshin Kim, M.D., Jihyang Lim, M.D., Eun-Jee Oh, M.D., Yonggoo Kim, M.D., Yeon-Joon Park, M.D., and Kyungja Han, M.D.corresponding author



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.


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.


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 218.19×109/L to 725.14×109/L. The errors were corrected by simple dilution with isotonic solution. However, the corrective WBC counts differed according to individual cases.


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 100.00×109/L, followed by reanalysis of the reticulocyte count and reticulocyte scattergram.

Keywords: Reticulocytes, Leukocytosis, Reticulocyte count

Articles from Annals of Laboratory Medicine are provided here courtesy of Korean Society for Laboratory Medicine