To the Editor.—Automated blood cell counters provide fast and reliable results and are present in virtually all clinical pathology laboratories. Some specific issues are raised during cell analysis and are flagged for laboratory staff analysis. The Sysmex XE-2100 series (Sysmex Corporation, Kobe, Japan) uses a flow cytometry method for cell count that is based on cell size, complexity, and staining of genetic material with a fluorescent dye. Specifically, basophils are identified from other granulocytes, based on frontal and side scattering of light. The reliability of this analyzer has been previously proved.1,2 However, under some circumstances, this analyzer may misinterpret data.3 In our laboratory routine, we had observed that basophilia almost never matched optical microscope counts. We proposed to identify the meaning of elevated basophil counts with the XE-2100. During 5 consecutive days, we analyzed all blood counts with automated basophil counts above 2% in 2 Sysmex XE-2100 and 2 XE-2100D systems. These data were compared with cell counts from optical microscope analysis. Statistical analysis was carried out with SPSS 13.0 software (SPSS Inc, Chicago, Illinois) for Microsoft Windows (Microsoft Corporation, Redmond, Washington). We received 11 281 samples for complete blood cell count in the 5-day period, of which 50 had basophilia, as defined above. Among all cell types, only atypical lymphocytes correlated with automated basophil counts (Pearson correlation, 0.728; P < .001) and no correlation was observed with basophil counts on optical microscopy. In this group of 50 complete blood cell counts, the “atypical lymphocyte” cell flag appeared in 41 cases and represented a higher count of this cell type (mean, 5.84 versus 0.55, P < .001). The “blast” flag appeared in 33 cases but did not imply a difference in mean for atypical lymphocyte count (5.45 versus 3.82, P = .26). Nevertheless, the presence of the “blast” flag defined a subgroup with higher incidence of atypical lymphocytes (Pearson χ2, P < .001). Therefore, basophilia must be considered with care in this Sysmex counter and almost always means atypical lymphocytosis. “Atypical lymphocytes” and “blasts” flags define, in this group, a subgroup with higher incidence of atypical lymphocytes. This pseudobasophilia phenomenon has already been described in Technicon4 (Bayer Diagnostics, Tarrytown, New York) and ADVIA 1205 (Siemens Medical Solutions Diagnostics, Tarrytown, New York) automated cell counters, but this is the first report of such findings in these Sysmex systems. Therefore, basophilia should be a criterion for blood smear review in clinical pathology laboratories that use XE-2100 series counters.
The authors have no relevant financial interest in the products or companies described in this article.