Morphologic Features of Peripheral Blood Smears in COVID-19 Infection

ABSTRACT

Background: At the end of 2019, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged as a novel coronavirus responsible for causing the global coronavirus disease 19 (COVID-19) pandemic. Symptoms range from asymptomatic to severe respiratory symptoms. SARS-CoV-2 infection is well known to be associated with immune dysregulation and hematologic aberrancies. Few studies have reviewed peripheral blood smears abnormalities from COVID-19 patients. In this study, we aimed to characterize the morphologic features of peripheral blood smears from COVID-19 patients. Design: Hospitalized patients with PCR-confirmed COVID-19 infection were identified. Complete Blood Count (CBC) data, clinical findings, and peripheral blood morphology were compared to control patients with confirmed negative COVID-19 PCR. Results: Twelve PCR confirmed covid 19 positive patients (male- 9, female- 3) with an age range 38 to 95 were compared to 11 control patients PCR-negative for COVID-19. Most patients presented with fever or respiratory symptoms. Among the COVID-19 positive patients absolute lymphopenia was seen in 9/12 patients. Absolute monocytosis was seen in 2/12 and monocytopenia was seen in 3/12 cases. Interestingly, large, activated monocytes with abundant gray-blue cytoplasm with prominent cytoplasmic vacuoles were seen in all the COVID-19 positive patents (see fig. 1 D-F) as compared to normal controls. These activated monocytes consist of 1-11% of leukocytes, with absolute counts ranging from 0.12-0.69 x 10∧3/microliter. Other morphologic findings found in peripheral blood smears include plasmacytoid and atypical lymphocytes (Fig 1A-C), as well as neutrophils with pseudo-Pelger-Huet nuclei (Fig 1G-I). 10/12 patients with COVID-19 infection were unvaccinated;differences between peripheral blood smears from vaccinated and unvaccinated patients were not seen. All patients recovered upon follow up. Conclusions: In conclusion, activated monocytes with distinct morphology are present in varying numbers in the peripheral blood from hospitalized COVID-19 patients. These activated monocytes are not present in non-COVID-19 patients. These findings are consistent with those found in previous studies. Some of these studies have shown the presence of activated monocytes may indicate favorable outcomes. (Figure Presented).