The Sysmex XN-2000 Hematology Autoanalyzer Provides a Highly Accurate Platelet Count than the Former Sysmex XE-2100 System Based on Comparison with the CD41/CD61 Immunoplatelet Reference Method of Flow Cytometry

Dear Editor The recently launched hematology autoanalyzer Sysmex XN2000 (Sysmex, Kobe, Japan) provides a new method (PLT-F method) for platelet counting based on a fluorescent RNA staining dye named oxazine [1, 2]. The main advantage of the XN2000’s PLT-F method over the former instrument XE-2100’s optical method (PLT-O method) is the ability to identify apoptotic white cells and not count them as platelets [2]. The XN-2000’s PLT-F method was reported to estimate platelets in thrombocytopenic samples more accurately than does the PLT-O method [1]. However, the performance of XN-2000’s PLT-F method still needs to be evaluated, including samples with broad range of platelet counts. We performed correlation and bias analyses comparing the platelet counts measured by the XN-2000 and XE-2100 autoanalyzers with those calculated by the immunoplatelet reference method (IRM) of flow cytometry. In total, 195 peripheral blood samples, which had been submitted for complete blood counts (CBC) at the authors’ institution between July and September 2013, were randomly selected for this study. All samples were analyzed using the XE2100 (PLT-O method) and XN-2000 (PLT-F method) autoanalyzers within 4 hr of sample collection. In addition, the platelet count was acquired by measuring CD41/CD61 IRM of flow cytometry using a FACSCanto II (Becton-Dickinson, Sunnyvale, CA, USA) [3]. This method uses the red blood cell (RBC): platelet ratio, which is calculated from RBC and platelet events measured by flow cytometry (Fig. 1A). Linear regression and Bland– Altman analysis were applied to compare the platelet counts measured by the two hematology autoanalyzers and those produced by CD41/CD61 IRM of flow cytometry. The platelet count-related parameters of the 195 samples obtained from the hematology autoanalyzers and by flow cytometry