What are the implications of elevated Complement (C') levels?

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Last updated: May 6, 2025View editorial policy

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From the FDA Drug Label

SOLIRIS, a complement inhibitor, increases the risk of serious infections caused by Neisseria meningitidis Patients receiving SOLIRIS are at increased risk for invasive disease caused by Neisseria meningitidis, even if they develop antibodies following vaccination

The use of eculizumab (IV), a complement inhibitor, may lead to an elevated risk of infections, including those caused by Neisseria meningitidis. However, the label does not directly address elevated complement levels.

  • The label discusses the increased risk of serious infections associated with the use of eculizumab (IV).
  • It emphasizes the importance of vaccination against meningococcal bacteria and monitoring for signs of infection.
  • The label does not provide information on the direct effect of eculizumab (IV) on complement levels 1.

From the Research

Elevated complement levels in the blood indicate an active inflammatory or immune response in the body, and treatment should focus on addressing the underlying cause rather than the elevated complement levels themselves. This finding is not a disease itself but rather a marker of underlying conditions such as infections, autoimmune disorders, or certain types of cancer. No specific medication is typically prescribed solely for elevated complement; instead, treatment focuses on addressing the underlying cause. If you have elevated complement levels, your healthcare provider should conduct a thorough evaluation including a complete medical history, physical examination, and possibly additional laboratory tests to identify the source of inflammation, as suggested by 2.

Common conditions associated with elevated complement include bacterial infections, viral hepatitis, rheumatoid arthritis, inflammatory bowel disease, and certain malignancies. The complement system is part of your innate immune defense, consisting of proteins that help antibodies and immune cells clear pathogens from the body. During active inflammation, the liver produces more complement proteins, leading to elevated serum levels, as explained in 3. Once the underlying condition is treated successfully, complement levels typically return to normal. Regular monitoring of complement levels may be recommended to track treatment effectiveness for the primary condition.

Some key points to consider when evaluating elevated complement levels include:

  • The complement system plays a crucial role in host defense and inflammation, as discussed in 4.
  • Complement activation results in opsonization of pathogens and their removal by phagocytes, as well as cell lysis, as noted in 4.
  • Inappropriate complement activation and complement deficiencies are the underlying cause of the pathophysiology of many diseases, such as systemic lupus erythematosus and asthma, as mentioned in 4.
  • The impact of complement dysregulation in atypical hemolytic uremic syndrome, paroxysmal nocturnal hemoglobinuria, and C3 glomerulopathies is also significant, as described in 2.

Overall, the most important step in managing elevated complement levels is to identify and treat the underlying cause of the inflammation, and this should be done under the guidance of a healthcare provider, with regular monitoring of complement levels as needed, as suggested by 5.

References

Research

Complement: an overview for the clinician.

Hematology/oncology clinics of North America, 2015

Research

The complement system.

Cell and tissue research, 2011

Research

Complement diagnostics: concepts, indications, and practical guidelines.

Clinical & developmental immunology, 2012

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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