Differential white blood cell count predicting severity and mortality in patients with COVID-19

Background: In coronavirus disease 2019 (COVID-19), the excessive inflammation is known to cause changes in blood parameters including differential white blood count and derived ratios such as neutrophil–lymphocyte ratio (NLR) and lymphocyte–monocyte ratio (LMR). Aim: To compare and analyze the association between differential white blood cell count and COVID-19 disease severity and mortality. Materials and methods: The study was a retrospective, observational study including 508 patients with confirmed COVID-19. Patients were divided into three groups based on severity. The laboratory parameters of all patients were collected and analyzed. Results: Among 508 patients, 75.6% were in mild, 9.1% were in moderate, and 15.4% were in severe categories. About 5.5% of the patients died during the treatment. The mean age of patients who got discharged was 42.47 ± 17.32 years and mean age of those who have died was 66.46 ± 14.37 years (P<0.001). When compared between all three groups and, between discharged and deceased, there were significant differences in mean neutrophils, lymphocytes, monocytes, NLR, and LMR (P<0.001). Neutrophilia, lymphopenia, and monocytopenia were associated with severe disease and increased mortality. Basophil count had no association with severity and mortality. A receiver operating characteristic curve of NLR for severe patients (area under the curve [AUC]: 0.951) and for deceased patients (AUC: 0.952) showed the ratio is significantly accurate in predicting severity and mortality, while that of LMR showed inverse association with severity and mortality. Conclusion: In patients with COVID-19, advanced age, neutrophilia, lymphopenia, and monocytopenia are associated with increased severity and mortality. High NLR and low LMR can be used as a marker for predicting the severity of the disease and mortality.