Association of complement pathways with COVID-19 severity and outcomes.

OBJECTIVES: Complement activation has been implicated in COVID-19 pathogenesis. This study aimed to assess the levels of complement activation products and full-length proteins in hospitalized patients with COVID-19, and evaluated whether complement pathway markers are associated with outcomes. METHODS: Longitudinal measurements of complement biomarkers from 89 hospitalized adult patients, grouped by baseline disease severity, enrolled in an adaptive, phase 2/3, randomized, double-blind, placebo-controlled trial and treated with intravenous sarilumab (200 mg or 400 mg) or placebo (NCT04315298), were performed. These measurements were then correlated with clinical and laboratory parameters. RESULTS: All complement pathways were activated in hospitalized patients with COVID-19. Alternative pathway activation was predominant earlier in the disease course. Complement biomarkers correlated with multiple variables of multi-organ dysfunction and inflammatory injury. High plasma sC5b-9, C3a, factor Bb levels, and low mannan-binding lectin levels were associated with increased mortality. Sarilumab treatment showed a modest inhibitory effect on complement activation. Moreover, sera from patients spontaneously deposited C5b-9 complex on the endothelial surface ex vivo, suggesting a microvascular thrombotic potential. CONCLUSION: These results advance our understanding of COVID-19 disease pathophysiology and demonstrate the importance of specific complement pathway components as prognostic biomarkers in COVID-19.

A Retrospective Study of COVID-19-Related Urgent Medical Visits and Hospitalizations After Outpatient COVID-19 Diagnosis in the US.

INTRODUCTION: Identifying risk factors for progression to severe COVID-19 requiring urgent medical visits and hospitalizations (UMVs) among patients initially diagnosed in the outpatient setting may help inform patient management. The objective of this study was to estimate the incidence of and risk factors for COVID-19-related UMVs after outpatient COVID-19 diagnosis or positive SARS-CoV-2 test. METHODS: Data for this retrospective cohort study were from the Optum® de-identified COVID-19 Electronic Health Record database from June 1 to December 9, 2020. Adults with first COVID-19 diagnosis or positive SARS-CoV-2 test in outpatient settings were identified. Cumulative incidence function analysis stratified by risk factors was used to estimate the 30-day incidence of COVID-19-related UMVs. Competing risk regression models were used to derive adjusted hazard ratios (aHR) and 95% confidence intervals (95% CI) for factors associated with UMVs. RESULTS: Among 206,741 patients [58.8% female, 77.5% non-Hispanic Caucasian, mean (SD) age: 46.7 (17.8) years], the 30-day incidence was 9.4% (95% CI 9.3-9.6) for COVID-19-related emergency room (ER)/urgent care (UC)/hospitalizations and 3.8% (95% CI 3.7-3.9) for COVID-19-related hospitalizations. Likelihood of hospitalization increased with age and body mass index, with age the strongest risk factor (aHR 5.61; 95% CI 4.90-6.32 for patients ≥ 85 years). Increased likelihood of hospitalization was observed for first presentation in the ER/UC vs. non-ER/UC outpatient settings (aHR 2.35; 95% CI 2.22-2.47) and prior all-cause hospitalization (aHR 1.90; 95% CI 1.79-2.00). Clinical risk factors of hospitalizations included pregnancy, uncontrolled diabetes, chronic obstructive pulmonary disease, chronic kidney disease, and autoimmune disease. A study limitation is that data on COVID-19 severity and symptoms were not captured. CONCLUSION: Predictors of COVID-19-related UMVs include older age, obesity, and several comorbidities. These findings may inform patient management and resource allocation following outpatient COVID-19 diagnosis.