ABSTRACT
Introduction: Coronavirus disease 2019 is caused by severe acute respiratory syndrome. Primarily an infection of the lower respiratory tract, it is now well known to cause multisystem abnormalities. Hematologic manifestations constitute a significant area of concern. Coronavirus disease 2019 causes lymphopenia, neutrophilia, and thrombocytopenia. Method(s): We explored the hemocytometric characteristics of Covid-19 pazients, using the Sysmex XN-1000 (Sysmex Corporation - Japan) hematology analyser and EDTA-anticoagulated peripheral blood sample. The analyzer utilizes fluorescence flow cytometry for the leukocyte differential count, allowing for enhanced subset differentiation based on size (forward scatter;FSC), internal structure/granularity (side scatter;SSC) and DNA/RNA content (fluorescence expression;SFL). Result(s): Despite a decrease in lymphocyte count, an increase in certain subpopulations of lymphocytes was observed in COVID-19. Indeed, reactive lymphocytes antibody-synthesizing and high fluorescence lymphocyte cells were higher as compared with controls. The so-called high fluorescence cells represent lymphoplasmacytoid B cells and plasma cells. These lymphocytes are responsible for the adaptive humoral immune response. In the present study, we observed that in addition to lower absolute count, lynfocytes of patients with COVID-19 were slightly larger in size. The fraction of reactive lynfocytes within the whole population were significantly increase in patiens with COVID-19 and showed a tipical pattern in hemocytometric plot where the reactive lynfocytes appare as isolated population, different from those observed in patients with mononucleosis. A perifheral blood film assesment on light microscope showed a distint population with the caracteristic morphology of plasma cells with abundant basophilic cytoplasm and an eccentric nucleus. Cytoplasmic and nuclear morphological anomalies, from hyposegmented nuclei to apopto-sis, have been observed in circulating granulocytes, associated with an increase in relative counts of immature cells. Conclusion(s): Patients withCOVID-19 showed both quantitative and qualitative differences in leucocyte populations. This study is an analysis of a typical pattern observed in Covid-19 patients using the Sysmex XN -1000 (Sysmex Corporation - Japan) hematology analyzer. The on going study will be the correlation with immunophenotipic and clinical characteristic of these patients to understand the morphological changes observed.