COVID-19 Pneumonia: when Do Eosinophils Matter?

Background: Since 2019, SARS-CoV-2 has become a global threat, causing millions of deaths. In addition, the mechanisms underlining pulmonary sequela remain not fully understood. Aim: to evaluate a possible association between serum values and radiological sequelae after discharge. Methods: 327 patients hospitalized for COVID-19 pneumonia were retrospectively enrolled and stratified on the basis of disease severity. Two blood tests were collected at hospital admission and at discharge, while radiological sequela was evaluated at the first follow-up visit (3 months). Δeosinophils was calculated as eosinophils at discharge - eosinophils at admission. Results: 214 patients were classified as low-intensity medical care (LIMC) and 113 as high-intensity medical care (HIMC). HIMC group was older [65(25–88)vs.60(22–87)years; p=0.01], with higher WBC count [6.9(1.63–19.15)vs.5.46(1.4–25.6)x10^9/L; p<0.0001], NLR [7.28(1.27–93.45)vs.4.05(0.73–41); p<0.0001] and CRP values [98(3.3 – 350)vs.43(2.9 – 270)mg/dl; p<0.0001] at hospitalization. Conversely, the LIMC group showed a higher eosinophil count [0(0–0.24)vs.0(0–0.14)x10^9/L; p<0.0001]. Considering Δeosinophils, both groups had increased values from hospitalization to discharge. However; Δeosinophils was higher in HIMC compared with LIMC patients [0.1(-0.03–0.72)vs.0.04(-0.15–0.3); p<0.0001]. In multivariable analysis, age ≥62 years (p=0.03) and Δeosinophils ≥0.05 (p=0.03) were two independent predictors of radiological lung sequelae in the whole population. Conclusion: the higher Δeosinophils level during hospitalization and older age were two independent risk factors of pulmonary sequelae at the first follow-up CT scan. Predictors of lung complications in COVID-19 are urgently needed.