Serum Immunoassay for Anti-Neutrophil Cytoplasmic Antibodies (ANCA) – Specific to Proteinase 3 (PR3)

This test measures the level of a specific substance or marker in your body, helping your healthcare team evaluate how well certain organs or systems are functioning and identify conditions that may require further medical attention.

The test detects the presence of anti-PR3 antibodies in your serum. PR3 (proteinase 3) is an enzyme stored in neutrophils. When the immune system mistakenly attacks these cells, it produces antibodies against PR3, which can be measured here. This is a key marker for a subset of autoimmune vasculitis, such as granulomatosis with polyangiitis (formerly known as Wegener’s granulomatosis).

Your doctor may order this test to help diagnose a medical condition, monitor an ongoing illness, check how well a current treatment is working, or rule out possible causes of symptoms you have been experiencing during your recent visits.

Your doctor may recommend this test if you have symptoms like persistent sinus or lung infections, kidney problems, or unexplained skin rashes. It’s also used to assess disease activity in patients already diagnosed with certain autoimmune conditions affecting blood vessels.

Before the test, your doctor will give you specific instructions, which may include fasting for a certain number of hours, avoiding certain medications or supplements, or drinking plenty of water. Tell your care team about all medicines you take and any allergies you have.

No special preparation is needed for this blood test. You may have a small needle inserted into your arm to draw blood. If you’re on blood thinners, let your doctor know before the test to avoid unnecessary precautions.

Possible results are usually described as normal, meaning your values fall within the expected range, or abnormal, meaning they fall outside that range. An abnormal result may point to an infection, a deficiency, or another condition, and your doctor will interpret it together with your symptoms, medical history, and other test findings.

Results are qualitative (positive or negative) rather than numeric. A positive result suggests a higher likelihood of autoimmune vasculitis involving PR3 antibodies, but further testing and clinical correlation are needed to confirm a diagnosis.