Anti-Proteinase 3 Antibody (ANCA) - Serum Immunoassay

What Is ANCA Testing Used For?

ANCA testing is primarily used to identify **anti-neutrophil cytoplasmic antibodies (ANCAs)**, which are linked to a group of autoimmune diseases called **vasculitides**. These conditions involve inflammation and damage to blood vessels, often affecting organs like the kidneys, lungs, skin, or digestive system. The test helps doctors determine if you may have a condition like **Wegener’s granulomatosis**, **microscopic polyangiitis**, or **chronic granulomatous disease**—though it’s not definitive on its own.

How Is the Test Performed?

A blood sample is drawn from a vein in your arm, usually in a doctor’s office or lab. The serum (liquid part of blood after clotting) is then tested using an **immunoassay** method to detect the presence of proteinase 3 antibodies. Results are reported as either **positive or negative** for these antibodies.

What Do Results Mean?

A positive result suggests a higher likelihood of vasculitis-related conditions, but it doesn’t confirm a diagnosis alone. Doctors may order additional tests (like imaging, kidney function tests, or biopsies) to confirm the diagnosis and guide treatment. False positives can occur, so results should always be interpreted by a healthcare provider.

Common Conditions Linked to ANCA Testing

Positive ANCA results are most strongly associated with **vasculitides**, including: - **Wegener’s granulomatosis** (affects lungs, sinuses, kidneys) - **Microscopic polyangiitis** (affects small blood vessels) - **Churg-Strauss syndrome** (lung and skin involvement) Other conditions (like certain infections or cancers) may also produce false positives, so clinical correlation is essential.