This test detects Complement C3a levels in the blood. The complement system in the blood contains over 30 proteins that play an important role in the body’s immune system. C3 accounts for roughly 70% of the proteins in the complement system. C3 can be divided into two parts: C3a and C3b. Measuring C3a levels can help with the diagnosis of a variety of diseases as well as distinguishing them from other conditions. Elevated C3a levels are common in people with asthma, autoimmune disorders like lupus, inflammatory diseases like pancreatitis, chronic hepatitis C, colon or liver cancer, inflamed pancreas, and Lyme disease. C3a levels in Lyme disease patients are typically elevated in recent acute infections but not in chronic infections.