Comparison of Impedance Platelet Count by Sysmex XE-5000

Background: Red blood cell (RBC) abnormalities are frequently found among thalassemia patients and have been reported to be a cause of spuriously high platelet counts. Objective: To compare impedance platelet count by Sysmex XE-5000 (PLT-XE) and Beckman Coulter LH 780 (PLT-LH) with optical fluorescent platelet count (PLT-O) in thalassemia patients. Methods: EDTA blood specimens from 152 thalassemia patients were analyzed by routine mode of PLT-XE and PLT-LH. The PLT-O run on reticulocyte mode of Sysmex XE-5000 was used as a reference method. Spearman’s rank correlation coefficient (rs ) and Bland-Altman plot were analyzed. Results: Correlations between impedance and PLT-O methods were excellent, as demonstrated by rs of 0.95 and 0.97 for PLT-XE and PLT-LH, respectively. However, there was no agreement between impedance and PLT-O methods. There were differences in biases of PLT-XE between thalassemia minor and both thalassemia intermedia and major. Compared to PLT-O, the concordance rates of diagnosis for platelet count abnormality were 94.7% and 96.7% for PLT-XE and PLT-LH, respectively. Conclusion: Compared to PLT-O, impedance method was associated with spuriously high platelet counts in thalassemia patients. Careful blood smear examination and/or accurate assay should be used in cases suspected of spuriously high platelet count.