Serum/plasma substance concentration for a specific protein marker (likely related to complement system)

What This Test Measures

The test detects the concentration of a specific complement component in your blood, which plays a role in immune defense. This protein is part of a cascade that helps clear pathogens and regulate inflammation. While the exact protein may vary by lab, it is often linked to conditions affecting immune response or chronic inflammation.

Why It’s Done

Your healthcare provider may order this test if you have symptoms like frequent infections, autoimmune conditions, or signs of overactive inflammation. It can also help diagnose or monitor certain inherited or acquired immune disorders.

Common Reasons for Testing

Possible triggers include suspected immune deficiencies, unexplained infections, or conditions like lupus, vasculitis, or chronic inflammatory diseases. Some labs may also use it to screen for genetic complement disorders.

Sample Collection and Preparation

A blood sample is drawn from a vein, typically in your arm. The blood is processed to separate serum or plasma, which is then sent to the lab for analysis. You may be asked to fast or avoid certain medications before the test, depending on the lab’s instructions.