---

Background and objectives: In patients with coronavirus disease 2019 (COVID-19), white blood cell (WBC) abnormalities have been found worldwide with significant inter-regional differences. In the present study, we evaluated WBC parameters concerning COVID-19 positivity and severity.
Methods: In this cross-sectional study, total WBC count, absolute count of each type of WBC, neutrophil to lymphocyte ratio (NLR), and lymphocyte to monocyte ratio (LMR) were compared between 150 COVID-19 patients and 150 non-COVID-19 patients presenting with COVID-19-like symptoms. Also, COVID-19 patients were divided into severe and non-severe cases.
Results: The severity of the disease had no significant association with age or gender (p>0.05). Total WBC count, absolute neutrophil count, absolute monocyte count, and NLR were significantly lower (p<0.05), while LMR was significantly higher in COVID-19 patients compared to non-COVID-19 patients (p<0.05). Total WBC count, absolute neutrophil count, and NLR were significantly higher (p<0.05), while absolute eosinophil count and absolute lymphocyte count were significantly lower (p<0.05) in severe COVID-19 patients compared to non-severe patients.
Conclusions: Age is not a predictive factor for the severity of COVID-19. Routine WBC parameters are useful in predicting the severity of the disease in COVID-19 patients and can be used as prognostic indicators. Routine WBC parameters can also be used for repeat RT-PCR testing in COVID-19 suspected patients.