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Updated: Dec 6, 2025
Measuring Erythrocyte Complement Receptor 1 Using Flow Cytometry
Published on: May 19, 2020
Decreased complement C3 levels are associated with poor prognosis in patients with COVID-19: A retrospective cohort
Shilin Fang1, Haizhou Wang2, Li Lu3
1Department of Pain, Renmin Hospital of Wuhan University, Wuhan 430060, China.
Insights
Low complement C3 levels in COVID-19 patients indicate a higher risk of in-hospital death. Monitoring complement C3 may aid in managing severe cases and suggests complement pathway inhibition as a potential therapy.
Area of Science:
- Immunology
- Virology
- Critical Care Medicine
Background:
- Coronavirus disease 2019 (COVID-19) is a global health crisis.
- Understanding the immune response in COVID-19 is crucial for patient management.
- Humoral immunity plays a significant role in the pathogenesis and outcomes of COVID-19.
Purpose of the Study:
- To characterize the humoral immune profile of patients diagnosed with COVID-19.
- To identify immune markers associated with severe outcomes, specifically in-hospital death.
- To explore potential therapeutic targets within the immune system for COVID-19.
Main Methods:
- Retrospective analysis of immunoglobulin (IgG, IgM, IgA, IgE) and complement (C3, C4) levels in 236 COVID-19 patients.
- Utilized univariable and multivariable logistic regression to identify risk factors for in-hospital mortality.
- Compared immune markers and clinical symptoms between survival and non-survival groups.
Main Results:
- Non-survivors exhibited significantly higher IgA and IgE levels, and lower complement C3 levels compared to survivors.
- Older age, elevated d-dimer, and decreased complement C3 were independent predictors of in-hospital death.
- Follow-up analysis showed C3 levels increased in survivors and decreased in non-survivors.
Conclusions:
- A low complement C3 level at admission serves as a critical alert for COVID-19 patients requiring intensified management.
- Targeting the complement pathway presents a promising therapeutic strategy for improving outcomes in COVID-19 patients.
- Further research into complement-mediated immunity in COVID-19 is warranted.
Objectives:
To describe the humoral immune feature of patients with coronavirus disease 2019 (COVID-19).
Methods:
The levels of total immunoglobulins (IgG, IgM, IgA, and IgE), complement (C3, C4) results were retrospectively analyzed in COVID-19 patients. Univariable and multivariable logistic regression were performed to explore the risk factors associated with the in-hospital death.
Result:
A total of 236 patients were enrolled in this study, of which 169 were transferred to another institution or discharged (survival group) and 67 died in hospital (non-survival group). Compared with survivors, the levels of IgA and IgE in non-survivors increased significantly, and level of complement C3 decreased. Non-survivors also showed higher incidence of chest tightness, breath shortness and dyspnoea; higher levels of inflammatory indicators, leukocytes and neutrophils; and low levels of lymphocyte subsets. Multivariable regression showed increasing odds of in-hospital death associated with older age (HR: 1.099; 95%CI: 1.057-1.143; p < 0.0001), d-dimer greater (HR: 1.294; 95%CI: 1.138-1.473; p < 0.0001) and decreased complement C3 level (HR: 0.073; 95%CI: 0.007-0.722; p = 0.025) on admission. Finally, in survival COVID-19 patients whose humoral immunity was re-examined, C3 levels tended to increase, while in non-survivors it decreased.
Conclusion:
Low level of complement C3 may be an alert to the admitted COVID-19 patients with additional management. Inhibition of the complement pathway might be an effective therapeutic to COVID-19 patients.
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