Minor side effects from the blood draw may include bruising, slight pain, or a small amount of bleeding at the site. Most people experience no serious complications. If you have a bleeding disorder or are on blood thinners, let your healthcare provider know before the test.
This test measures the level of antibodies against Proteinase 3 (PR3) in your blood. These antibodies are linked to a specific type of autoimmune condition.
["This test helps diagnose or monitor a rare but serious autoimmune disease called granulomatosis with polyangiitis (GPA)."]
Key facts at a glance
- LOINC
- 48408-9
- Short code
- Proteinase3 IgG Ser-aCnc
- Synonyms
- Proteinase3 IgG Ser-aCnc
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- CPT
- 82784
- Specimen volume
- 5 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 4–24 hours
- Order
- routine
Why This Test Might Be Ordered
Your healthcare provider may recommend this test if you have symptoms such as persistent sinus or lung infections, blood vessel inflammation, or other signs of a systemic autoimmune disease. It is often used alongside other tests to confirm a diagnosis of granulomatosis with polyangiitis or to check for disease activity in patients already diagnosed.
What to Expect Before the Test
No special preparation is needed for this blood test. You may have a small needle inserted into your arm to draw blood, which usually takes a few minutes. You can eat and drink normally before the test.
What the Test Results Mean
High levels of PR3 IgG antibodies may indicate an active autoimmune condition affecting blood vessels. Your doctor will interpret the results in the context of your symptoms, medical history, and other test results. Elevated levels can help guide treatment decisions.
Common Reasons for Monitoring
If you have been diagnosed with granulomatosis with polyangiitis or another related condition, this test may be used to monitor disease activity over time. Regular testing helps assess how well your treatment is working and whether adjustments are needed.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Clinical Significance
Short name
PR3 IgG Antibody (Serum)
Frequently asked questions
Elevated PR3 IgG antibodies are strongly associated with granulomatosis with polyangiitis (formerly known as Wegener’s granulomatosis), an autoimmune disease that targets blood vessels. This test is critical for diagnosis and management because early detection improves treatment outcomes. It is not specific to GPA alone, so results should be reviewed with other clinical findings.
A positive result (meaning elevated antibody levels) suggests a higher likelihood of granulomatosis with polyangiitis or a related vasculitis. However, it is not definitive on its own. Your doctor will consider your symptoms, medical history, and possibly other tests to make a diagnosis. False positives can occur in some cases, so further evaluation may be needed.
Yes, this test can be used to monitor disease activity. Repeated testing over time can help determine whether your condition is improving, stable, or worsening. Your doctor may adjust treatments based on these results, especially if you are receiving immunosuppressive therapy.
Sources
- 1
- 2Lab Tests OnlineSource
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy