Serum Proteinase 3 (PR3) Antibody, Quantitative

Why This Test Is Done

Your healthcare provider may order this test if you have symptoms of vasculitis—a condition where blood vessels become inflamed—and have been diagnosed with or are suspected of having **cryoglobulinemia** or **microscopic polyangiitis**, two autoimmune-related blood vessel diseases. It may also be used to assess active disease or guide treatment decisions.

What to Expect Before the Test

No special preparation is needed. You may eat and drink normally. The blood sample is typically taken from a vein in your arm, similar to other routine blood tests.

What the Test Results Mean

High levels of PR3 antibodies may indicate an active autoimmune response. However, results alone do not diagnose the condition; they are usually interpreted alongside clinical findings, other tests, and patient symptoms. Your doctor will discuss the results in the context of your overall health.

Common Conditions Linked to PR3 Antibodies

Elevated PR3 antibodies are most strongly associated with **microscopic polyangiitis**, a type of vasculitis that affects small blood vessels. They can also be found in other autoimmune conditions, but less commonly. Your doctor will consider the full clinical picture when determining significance.