Study of the morphologic changes in the peripheral blood smear as a predictive tool for the early diagnosis of coronavirus disease 2019 and their relation to the clinical course severity

Introduction Coronavirus disease 2019 (COVID-19) infection affects different organs of the human body, and also the blood cells. Since the beginning of the COVID-19 pandemic, many studies have described the quantitative peripheral blood findings seen in COVID-19 patients. However, morphologic changes have been described by only a few studies. Peripheral blood smear (PBS) is a simple and available method to investigate blood cells’ morphologic changes. Aim In this study, we aimed to determine the morphologic changes affecting all blood cells of COVID-19 patients and their relation to the early diagnosis and the patients’ clinical course severity. Patients and methods PBS of 200 COVID-19 patients and 50 non-COVID-19 controls was examined for morphological changes in the period between January 2021 and January 2022, the patients’ clinical course and blood chemistry were reported. Results Significant morphological changes were found. Smudge cells are the most frequent. Other findings were schistocyte, increased large granular lymphocytes, leukoerythroblastic reaction, pseudo Pelger–Huët, abnormal monocytes, and giant platelets. Our results showed significant relationship between PBS findings and the clinical course severity and outcome.