Comparison of Sysmex DI-60 digital optical microscopy and manual optical microscopy in leukocyte differentiation

Manual microscopic differentiation of leukocytes is the primary tool for the diagnosis and monitoring of various diseases. Recently, digital optical microscopy has become a more common method, being an alternative to the conventional one, and therefore, there is a need to investigate its compatibility in more detail. The objective is to compare the results of digital and manual microscopy in the analysis of different leukocyte types and to assess the linearity, systemic and proportional differences between the methods. 109 samples were analyzed by manual and digital microscopy (Sysmex DI-60), and the comparison of the obtained results was performed by Passing-Bablok and Bland-Altman analysis. The linearity of the methods is satisfactory in all cells, except basophils and blasts. A statistically significant systemic difference was detected in segmented neutrophils, immature granulocytes, and lymphocytes, and correlations between the methods range from very strong to moderate, depending on the type of cells. Significant deviations were observed in leukocytosis and leukopenia. The results of the conducted analysis indicate a good correlation between digital and manual microscopy, but the identified systemic and proportional differences indicate the significance of the reclassification offered by the analyzer. In cases of severe leukopenia and leukocytosis, it is recommended to use manual microscopy as an additional check.