Quantitative and qualitative changes in blood cells associated with COVID-19

Aim To establish the relationship of hematological disorders with the pathogenesis, course and outcomes of COVID-19 Methods We examined 235 hospitalized patients with moderate and severe forms of acute COVID-19 receiving anticoagulants and immunosuppressive drugs We studied the full blood cell counts and morphology along with the platelet function by flow cytometry in comparison with the clinical features and synthesis of inflammatory markers To assess platelet contractility, blood clot contraction (retraction) kinetics was used in combination with scanning electron microscopy of platelets and blood clots Results Hemolytic anemia, neutrophilia and lymphopenia were associated with immature erythrocytes and leukocytes, indicating activation of hematopoiesis Contraction of blood clots in COVID-19 was impaired, especially in severe and lethal cases, as well as in the presence of comorbidities, including myeloproliferative and coronary heart diseases and acute cerebrovascular disease In male patients, the changes in clot contraction were more pronounced Suppression of clot contraction correlated directly with anemia and coagulopathy, including a high D-dimer level, which confirms the pathogenetic significance of blood clot contraction in COVID-19 A decrease in platelet contractility was due to moderate thrombocytopenia in combination with chronic platelet activation and secondary platelet dysfunction The structure and cellular composition of blood clots depended on the extent of contraction;clots with impaired contraction were porous, had a low content of deformed polyhedral erythrocytes (polyhedrocytes) and an even distribution of fibrin Conclusion Blood cells undergoing both quantitative and qualitative changes are involved in the pathogenesis of COVID-19;the suppressed platelet-driven contraction of intravital blood clots may be a part of the prothrombotic mechanisms © 2021 The Author(s) This is an open-access article distributed under the terms of the Creative Commons Attribution 4 0 International License (CC-BY 4 0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited See http://creativecommons org/ licenses/by/4 0/