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Circulating complement proteins in patients with sepsis or systemic inflammatory response syndrome
1Institute of Medical Microbiology, Medical School Hannover, Germany.
Insights
Measuring C3a levels and the C3a/C3 ratio in plasma can help diagnose sepsis early and assess patient prognosis. Elevated C3a and C3a/C3 ratios were observed in intensive care unit patients upon admission.
Area of Science:
- Immunology
- Critical Care Medicine
- Biochemistry
Background:
- Sepsis triggers a significant activation of the complement system, a key early event in the syndrome.
- Early diagnosis of sepsis is crucial for effective treatment and improved patient outcomes.
Purpose of the Study:
- To investigate the utility of plasma complement components C3a, C5a, and C3, and the C3a/C3 ratio for early sepsis diagnosis.
- To assess the potential of these markers in differentiating sepsis from systemic inflammatory response syndrome (SIRS) and predicting prognosis.
Main Methods:
- Plasma levels of C3a, C5a, and C3 were measured in 33 intensive care unit patients and healthy donors over 10 days.
- Patients were monitored for clinical and microbiological criteria of sepsis and SIRS.
- Statistical analyses were performed to compare marker levels between groups and correlate them with clinical outcomes.
Main Results:
- Intensive care unit patients exhibited significantly elevated C3a levels and C3a/C3 ratios upon admission compared to healthy donors (P < 0.0001).
- C3 levels were significantly reduced on admission but increased during the study (P < 0.0001). C5a levels showed no significant difference.
- C3a levels and C3a/C3 ratios differentiated sepsis patients from those with SIRS within 24 hours of sepsis onset (P < 0.05).
- Higher C3a levels were observed in non-survivors compared to survivors (P = 0.0185).
Conclusions:
- Plasma C3a concentration and the C3a/C3 ratio are valuable biomarkers for early sepsis diagnosis.
- These markers can aid in distinguishing sepsis from SIRS and serve as a prognostic indicator.
- C3a measurement offers a promising tool for improving sepsis management in critical care settings.
Abstract:
The systemic inflammatory response of the body to invading microorganisms, termed sepsis, leads to profound activation of the complement system. Pathophysiological concepts suggest that complement activation occurs very early in this syndrome. Thus, we discuss whether the determination of concentrations of the complement components C3a, C5a, and C3 in plasma as well as of the C3a/C3 ratio might be helpful to diagnose sepsis early. For this purpose, 33 patients from an intensive care unit were monitored for 10 days. In comparison with healthy donors, C3a levels and the C3a/C3 ratio of intensive-care-unit patients were significantly elevated (P < 0.0001) on admission. In contrast, C3 levels were significantly reduced (P < 0.0001) but increased during the study. C5a levels in the plasma of healthy donors and patients were identical. Twenty-two of 33 patients fulfilled microbiological and clinical criteria of sepsis. Eleven patients had signs of systemic inflammatory response syndrome but no microbiological evidence of sepsis. The groups could be differentiated from each other by their C3a levels or their C3a/C3 ratios during the first 24 h after the clinical onset of sepsis (P < 0.05). Septic patients in shock had higher C3a levels than normotensive septic patients, although the differences were not significant. Nonsurvivors had significantly higher C3a levels on admission than survivors (P = 0.0185). No differences were found between septic patients who developed adult respiratory distress syndrome and those who did not. Thus, determination of C3a concentrations in plasma may prove useful (i) to diagnose sepsis early, (ii) to differentiate between patients with sepsis and those with systemic inflammatory response syndrome, and (iii) to assess prognosis.