Complement component 3 (C3)

Performed when there is suspicion of autoimmune diseases, such as systemic lupus erythematosus (SLE), rheumatoid arthritis, or glomerulonephritis. They help assess the activity of the complement system, which plays a role in inflammation and immune response. Symptoms that may prompt these tests include unexplained infections, fatigue, joint pain, and signs of inflammation. Low levels may indicate active disease or increased complement consumption.