Relationship of eosinophil level with severe COVID-19 outcomes in asthma of the elderly

There is a significant decrease in the eosinophil level of patients’ peripheral blood in COVID-19, and in most of them — at an early stage, regardless of the disease’s severity. It is believed that patients with bronchial asthma have a lower risk of adverse outcomes of COVID-19, and eosinophilia, both in patients with and without asthma, is associated with a reduced risk of mortality. Objective. To study the relationship of eosinophil level with the outcomes of severe COVID-19 in bronchial asthma of the elderly. Material and methods. The study included elderly patients (>60 years old (according to WHO classification, 2020), n=76) with documentally confirmed history of bronchial asthma (according to GINA criteria, 2020), hospitalized for severe COVID-19. Presence of COVID-19 was confirmed by laboratory tests (polymerase chain reaction) and/or clinically and radiologically. The patients were monitored at the hospital stage and within 1 month after discharge from the hospital. Calculation of odds ratio and 95% confidence intervals (95% CI) was done using single-factor and multi-factor logistic regression (IBM SPSS Statistics v. 22 application software package). Results. Analysis of eosinophil level depending on the disease’s outcome (survived/died) has shown that the median of eosinophil level in the group of survived patients was 30 [10; 100] (95% CI 13—60) cells/µL, and in the group of deceased — 16.5 [9; 39] (95% CI 11—29) cells/µL, the differences were statistically significant (p=0.04). The level of eosinophils above 100 cells/µL is associated with a favorable outcome of the disease, and the chance of survival at such eosinophil level is 13.5 (95% CI 1.6—242) times higher than at the level of eosinophils <100 cells/µL. Considering the multivariate adjustment, increased eosinophil level (>100 cells/µg) was associated with lower glucose level (<7 mmol/L), lactate dehydrogenase (LDH) (<450 U/L) and respiratory rate (<23 per minute), thus the relationship between the chance of survival and eosinophil level remained statistically significant — OR 32.1 (95% CI 1.1—141) (p=0.04). Despite the existing relationship between the level of eosinophils and mortality, the relationship between the absolute number of eosinophils and the duration of hospitalization was not revealed. Conclusion. Elevated level of eosinophils in bronchial asthma of the elderly and severe COVID-19 is associated with a favorable outcome of the disease.