Background: A decrease in eosinophil levels was found in Corona Virus Disease-19 [COVID-19] patients [eosinopenia]. However, recent research on eosinopenia and disease severity has yielded conflicting results.
Objectives: To investigate the relationship between interleukin [IL]-5 and IL-6 levels, COVID-19 severity, and eosinophil count in Egyptian patients.
Patients and Methods: Eighty-three COVID-19 patients were enrolled. At hospital admission, patients' medical records were reviewed for sociodemographic, clinical, and laboratory data. IL-5 and IL-6 levels in pretreatment serum samples were measured by enzyme linked immunosorbent assay [ELISA].
Results: Severe disease patients had significantly lower eosinophil levels than non-severe patients [0.0 ×10³/μL [0.0-0.4] vs. 0.2×10³/μL [0.0-0.4]; P ≤ 0.001]. On the other hand, levels of IL-5 [180.0 pg/ml [10.0-960.0] vs. 300.0 pg/ml [170.0-690]; P=0.013] and IL-6 [110.0 pg/ml [20.0-600.0] vs. 45.0 pg/ml [20.0-120.0]; P ≤ 0.001] were significantly higher. Additionally, eosinophils were significantly negatively correlated with biomarkers of coagulation dysfunction [D-dimer; P=0.016], inflammation [C-reactive Protein [CRP]; P=0.037 and ferritin; P=0.049] and cytokine storm [IL-6; P=0.018], but there was no significant correlation between eosinophils and IL-5 [P=0.931]. In addition, eosinophil count showed little diagnostic significance in distinguishing between severe and non-severe COVID, with an area under the curve [AUC] of 0.174.
Conclusion: Anti-COVID-19 immunotherapy could target IL-5, IL-6, and eosinophils. IL-6 levels outperformed IL-5 levels and the peripheral eosinophil count in predicting COVID-19 development. Despite its weak predictive potential, eosinopenia has been related to severe COVID-19 infection and a higher risk of in-hospital death.