Screening of Peripheral Blood Film for Abnormalities in Leucocyte Morphology in Mild to Moderate COVID-19: A Promising Screening Tool for Guiding Quick Clinical Diagnosis in Outpatient Clinics

Objective: Abnormal leucocyte count, namely neutrophilia, lymphopenia and even eosinopenia is well documented in COVID-19 patients. But the morphological changes in leucocytesare chronicled in few studies and mostly in hospitalized cases. We endeavored to study the morphological changes in neutrophils, lymphocytes and monocytes in confirmed COVID-19 cases with mild to moderate symptoms as well as asymptomatic contacts presenting at an outpatient clinic. Material and methods: The study included 36 COVID-19 diagnosed cases, including 30 patients with mild to moderate symptoms and six asymptomatic contacts, presenting at an outpatient clinic. The venous blood samples collected at presentation were run on three-part hematology analyzer and peripheral blood films were examined by a pathologist for morphological abnormalities in WBCs. Results: The total leucocyte count was within normal reference range in all except one patient. Although neutrophilia and lymphopenia were evident in 25% of cases, PBF examination revealed constellation of morphological changes in leucocytes in all cases, including asymptomatic contacts. Nuclear spikes (80%), abnormal nuclear shapes and segmentation (75%) in neutrophils were frequently observed. Howell-Jolly body like inclusion in neutrophils was a noteworthy finding in one-third patients. Reactive/ plasmacytoid lymphocytes and abnormal coalescent cytoplasmic vacuoles in monocytes were observed in nearly half of our patients. Conclusion: COVID-19 induces a wide range of quantitative and qualitative changes in both granulocytes and agranulocytes, even in patients with mild symptoms and asymptomatic contacts.