biostudies-literatureUnknown14Xu Z<h4>Background</h4>A few studies found that the complement system may be involved in the onset and progression of community-acquired pneumonia (CAP). However, the role of the complement system in CAP was obscure. The goal of this study was to analyze the association of serum complement C3a with CAP severity scores based on a cross-sectional study.<h4>Methods</h4>All 190 CAP patients and 95 control subjects were enrolled. Demographic information and clinical data were extracted. Peripheral blood samples were collected on admission.<h4>Results</h4>Serum complement C3a on admission was elevated in CAP patients compared with healthy subjects. The level of complement C3a was gradually elevated in parallel with CAP severity scores (CURB-65, CRB-65, PSI, SMART-COP, and CURXO). Complement C3a was Frontiers in immunology1034233https://www.ebi.ac.uk/biostudies/studies/S-EPMC9911530biostudies-literatureThe association between serum complement C3a and severity in patients with community-acquired pneumonia.PMC9911530Zheng LFeng CMXu DXFu LXu ZHou XFZhao HfalseThe association between serum complement C3a and severity in patients with community-acquired pneumonia.<h4>Background</h4>A few studies found that the complement system may be involved in the onset and progression of community-acquired pneumonia (CAP). However, the role of the complement system in CAP was obscure. The goal of this study was to analyze the association of serum complement C3a with CAP severity scores based on a cross-sectional study.<h4>Methods</h4>All 190 CAP patients and 95 control subjects were enrolled. Demographic information and clinical data were extracted. Peripheral blood samples were collected on admission.<h4>Results</h4>Serum complement C3a on admission was elevated in CAP patients compared with healthy subjects. The level of complement C3a was gradually elevated in parallel with CAP severity scores (CURB-65, CRB-65, PSI, SMART-COP, and CURXO). Complement C3a was 2023-01-01T00:00:00Z20232025-04-25T19:23:39.012Z2025-04-06T07:57:46.689ZS-EPMC99115303677683410.3389/fimmu.2023.1034233