Description
Overview:
Complement C3 is the most abundant protein in the complement system—a complex part of the immune system that helps antibodies and phagocytic cells clear pathogens from an organism. C3 plays a central role in activation pathways that lead to the destruction of bacteria and viruses.
Clinical Significance:
Measuring C3 levels helps physicians understand immune system activity.
Low C3 Levels: Often indicate that the complement system is being “consumed” or used up faster than it can be produced due to active inflammation or autoimmune processes. This is commonly seen in active Systemic Lupus Erythematosus (SLE), certain types of kidney disease ( glomerulonephritis), and severe fungal or parasitic infections.
High C3 Levels: Because C3 is an “acute-phase reactant,” levels can rise during acute inflammation, trauma, tissue necrosis, or chronic infections.
When is this test recommended?
To help diagnose autoimmune disorders like lupus (SLE) or rheumatoid arthritis.
To monitor disease activity in patients with known autoimmune conditions (falling C3 levels often signal a flare-up).
To investigate unexplained inflammation or kidney dysfunction.
To evaluate patients with recurrent, unexplained bacterial infections.
Sample Requirements:
Specimen: Serum.
Container: Gold Top (SST) or Red Top Tube.
Preparation: No fasting is typically required, though standard lab protocols may vary.
