Characteristics of Inflammatory Storm in BALF of Severe Pneumonia in Children: A Case Control Study

Abstract Background: It is difficult to collect bronchoalveolar lavage fluid (BALF) from children. There are few studies on inflammatory storms in BALF of children with pneumonia. Therefore, we will retrospectively investigate characteristics of inflammatory storms in BALF of children with pneumonia in our hospital.Methods: This retrospective study included 161 children with pneumonia. Pediatric pneumonia was divided into two groups: mild and severe pneumonia, according to the clinic diagnosis. All clinic information and data came from our hospital’s database. Blood and BALF samples were collected and measured by Clinical laboratory and Clinical Molecular Medical Center. Flow cytometry was performed to detect the levels of cytokines, including IL-2, IL-4, IL-6, IL-10, IL-17A, TNF-α and IFN-γ. We performed receiver operator characteristic curve (ROC) and spearman correlation to evaluate the role of BALF inflammatory cytokines and cells in pneumonia.Results: 1) The levels of IL-6, IL-10, IL-17A, and TNF-α, and ratios of IL-6 to IL-10 and TNF-α to IL-10 in BALF of severe pneumonia group were higher than those of mild pneumonia group. 2) The number of inflammatory cells and the percentage of neutrophils in BALF of severe pneumonia group increased, and the percentage of macrophages decreased, compared with the mild pneumonia group. 3) ROC analysis showed that the levels of IL-6, IL-10 and TNF-α, and ratios of IL-6 to IL-10 and TNF-α to IL-10, the number of inflammatory cells and neutrophils, as well as the percentage of neutrophils exceeded the cut-off value (60.37pg/mL, 2.54pg/mL, 13.07pg/mL, 29.30, 1.57, 3140.00*109/L, 768.00*109/L, 43.00%, respectively) could be used to distinguish children with severe pneumonia from children with mild pneumonia. While the percentage of macrophages in BALF decreased to below the cut-off value (36.00%) also had the discrimination ability. 4) The BALF levels of IL-6, IL-10, TNF-α and IFN-γ were correlated, positively with the inflammatory cell count and the percentage of neutrophils, and negatively with the percentage of macrophages.Conclusion: In severe pediatric pneumonia, BALF inflammatory cytokines and inflammatory cell infiltration are more intense, especially above the cut-off value. This study demonstrates that these inflammatory signals are potential biomarkers for predicting the severity of pediatric pneumonia.Trial registration: This study approved by the Medical Research Ethics Committee of Children’s Hospital of Chongqing Medical University, registered in http://www.chictr.org.cn/, No. ChiCTR2000034048(registration date, June 22, 2020).