White Blood Cells in COVID-19: A Study on Viral Induced Cytopathic Changes in the Peripheral Smear

Introduction: Laboratory parameters are crucial in diagnosis and prognosis of Coronavirus Disease 2019 (COVID-19). It would be of interest to explore morphological changes in infected White Blood Cells (WBCs). A detailed examination of peripheral smears may shed light on pathophysiology of infected cell lines and differentiate them from those in established viral infections like dengue and infectious mononucleosis.

Aim: To study morphological changes of WBCs in peripheral smears of severe and non severe cases of COVID-19 patients.

Materials and Methods: This cross-sectional study was conducted at a tertiary care centre, Dr. Chandramma Dayananda Sagar Institute of Medical Education and Research, Ramanagara, Karnataka, India, from April 2021 to August 2021 on 120 peripheral smears of adult COVID-19 positive cases. Abnormal morphological features were graded by counting 100 cells in each of neutrophils, lymphocytes and monocyte lineage. Changes were compared and analysed between severe and non severe groups using Statistical Package for Social Sciences (SPSS) software version 26.0. A p-value <0.05 was considered as significant.

Results: The study included total of 120 cases (59 severe and 61 non severe) with a mean age of 47 years. Male to female ratio in severe and non severe categories were 1:1.2 and 1:0.6, respectively. Severe category patients (n=59) were associated with statistically significant leucocytosis (p-value=0.04), absolute neutrophilia (p-value=0.03) and higher grades of morphological changes- abnormal nuclear morphology (p-value=0.002) and Pseudo-Pelger-Huët anomaly in neutrophils (p-value=0.029), plasmacytoid lymphocytes (p-value=0.03), cytoplasmic granularity and atypical lymphocytes (p-value=0.04). Monocytes showed large coalescent vacuoles and cytoplasmic granules (p-value=0.03). Though present in non severe category (n=61), they were proportionately of lesser grades.

Conclusion: Viral cytopathic effects in WBC lines on peripheral smear had significant clinical implications on disease severity, undermining need for a comprehensive study of viral induced morphological changes in hospitalised COVID-19 patients.