Behavior of Eosinophil Counts in Recovered and Deceased COVID-19 Patients over the Course of the Disease

Abstract

Knowledge about the immune responses against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, particularly regarding the function of eosinophils, has been steadily emerging recently. There exists controversy regarding the implications of eosinophils in the coronavirus disease 2019 (COVID-19)’s pathology. We report a retrospective cohort study including the comparison of leukocyte counts in COVID-19 patients, considering the outcomes of recovery (n = 59) and death (n = 60). Among the different types of leukocytes, the eosinophil counts were those that showed the greatest difference between recovered and deceased patients. Eosinopenia (eosinophil count < 0.01 × 109/L) was more frequently observed in deceased than recovered patients (p = 0.0012). The eosinophil counts more rapidly increased and showed a greater proportion over the course of the disease in the recovered than deceased patients. Furthermore, the estimated survival rate was greater in patients without eosinopenia than in patients with eosinopenia (p = 0.0070) during hospitalization. Importantly, recovered but not deceased patients showed high negative correlations of the eosinophils with the neutrophil-to-lymphocyte ratio (NLR) and neutrophil counts at Day 9 of the onset of clinical symptoms (p ≤ 0.0220). Our analysis suggests that eosinopenia may be associated with unfavorable disease outcomes and that the eosinophils have a beneficial function in COVID-19 patients, probably contributing by controlling the exacerbated inflammation induced by neutrophils.

Characteristics of peripheral white blood cells in COVID-19 patients revealed by a retrospective cohort study

“…Previous study demonstrated that severe patients tend to have lower lymphocytes counts, higher leukocytes counts and neutrophil–lymphocyte-ratio (NLR), as well as lymphopenia has been reported as a predictor of prognosis in COVID-19 patients [ 9 , 14 , 15 ]. Our data also revealed that the initial counts of lymphocytes, eosinophils, and basophils of COVID-19 patients were much lower in non-survivors compared with the counts of above indices in survivors, which was consistent with conclusion of other studies [ 11 , 12 ].…”

“…Several cohort studies have reported that lymphopenia can predict prognosis in COVID-19 patients [ 9 , 10 ]. In addition, a few studies found that the eosinopenia was also associated with poor prognostic features [ 11 , 12 ]. Thus, the differentiation of peripheral white blood cells may indicate the immunologic impairment at the early stage of the disease.…”

Routine laboratory parameters, including complete blood count, predict COVID-19 in-hospital mortality in geriatric patients

“…Interestingly, our results showed a significant association between low eosinophil counts and COVID-19 severe outcomes. It was suggested that eosinophils could play beneficial functions in COVID-19 patients, probably contributing by controlling the exacerbated inflammation induced by neutrophils ( Cortes-Vieyra et al, 2021 ). Even if the role of eosinophils in inflammation remains controversial, recent evidence suggested that different eosinophils subpopulations in the same tissue could differentially modulate inflammatory responses ( Kanda et al, 2021 ).…”

Asthma as a risk factor for hospitalization in children with COVID‐19: A nested case‐control study

“…We also found that children with asthma presenting with COVID‐19 had lower eosinophil counts and fewer atopic comorbidities than asthma controls. Eosinopenia has been associated with worse outcomes and mortality in adult COVID‐19 36,37 . Eosinophils play an important role in the immune response to respiratory viruses; atopic patients with higher eosinophil counts may be somewhat “protected” from SARS‐CoV‐2 infection, 38 and A+C cases with relatively lower counts may have thus been more susceptible.…”