ArticleBMC infectious diseases2025
Impact of complement system proteins on the clinical progression of hospitalized patients with COVID-19.
Article in BMC infectious diseases, 2025. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 2 papers.
What it found
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The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.
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Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.
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Who cites it
2 citing papers in PubMed.
- Ventilator-Associated Pneumonia: The Role of Kidney-Lung Crosstalk and Renal Replacement Therapy, a Narrative Review.Journal of clinical medicine · 2026Review
- The Complement System in the Setting of Critical Illness-A Narrative Review.Biomolecules · 2026Review
Corrections and comments
PubMed lists nothing against this paper. Absence here is not a guarantee, only a check that was made.
Authors and funding
6 authors.
Funding
Abstract
backgroundThe complement system is an important defense mechanism against pathogens, including viruses. In COVID-19, evidence suggests that hyperactivation of the complement system can lead to tissue damage and provoke dysregulation of the coagulation cascade, resulting in vascular damage observed in severe COVID-19. There is still little evidence regarding the role of plasma levels of these molecules in the clinical evolution of hospitalized patients with COVID-19.
methodsThe study included individuals 18 years of age or older with confirmed diagnosis of COVID-19, admitted to two referral hospitals in the Northeast Region of Brazil between August 2020 and July 2021. Plasma samples were collected within 24 hours of hospital admission. Patients were followed up until discharge, and complications during hospitalization were duly recorded. Plasma levels of the following complement proteins were determined by Luminex: C2, C3, C3b/iC3b, C4, C4b, C5, C5a, MBL, C1q, factor I, factor D, factor B, and factor H. A multivariate logistic regression analysis was used to correct the results according to possible confounding factors.
resultsThe study included 267 patients (134 critical and 133 severe), with mean ages of 54 and 52 years, respectively. Plasma levels of C2, C5a, factor B, and factor D were significantly higher in patients who required intensive care unit admission, required ventilatory support, developed sepsis, developed cardiorespiratory arrest, or developed acute kidney failure. On the other hand, C4b level was lower in patients who developed complications. Complement proteins were significantly associated with laboratory parameters related to coagulation and kidney function.
conclusionThese findings show that the complement system is associated with COVID-19 complications and laboratory parameters of coagulation and kidney function. These results suggest that these molecules may be potential biomarkers or therapeutic targets in the clinical progression of COVID-19.
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