Serum Anti-Proteinase 3 Antibody (ANCA) by Immunofluorescence
This test measures antibodies against a protein called proteinase 3 (PR3) in your blood. These antibodies are linked to a type of autoimmune condition called granulomatosis with polyangiitis (GPA), also known as Wegener’s granulomatosis.
["This test helps diagnose or monitor certain autoimmune diseases affecting blood vessels."]
Key facts at a glance
- LOINC
- 54156-5
- Short code
- RNAp I Ab Ser Ql IF
- Synonyms
- RNAp I Ab Ser Ql IF
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- if
- 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
What This Test Measures
The test detects the presence of antibodies directed against proteinase 3, a protein found in white blood cells. These antibodies are part of a broader class called antineutrophil cytoplasmic antibodies (ANCAs), which are associated with specific autoimmune conditions.
Why It’s Done
Your healthcare provider may order this test if you have symptoms like persistent sinus or lung infections, kidney problems, or unexplained skin rashes. It’s often used alongside other tests to diagnose conditions like granulomatosis with polyangiitis or microscopic polyangiitis.
How It’s Performed
A blood sample is taken from a vein in your arm. The serum (liquid part of blood) is then examined under a microscope to identify the presence of anti-PR3 antibodies using immunofluorescence techniques.
What to Expect Before the Test
No special preparation is needed. You may have some mild discomfort or bruising at the injection site, but this usually goes away quickly. If you’re on blood-thinning medication, let your provider know before the test.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Positive results for anti-PR3 antibodies strongly suggest granulomatosis with polyangiitis or other related autoimmune vasculitis. While this test is highly specific for certain conditions, it should be interpreted alongside clinical symptoms, other test results, and patient history. False positives can occur, so further evaluation may be needed.
Short name
Anti-PR3 Antibody (ANCA)
Frequently asked questions
What does a positive result mean?
Can I fast before this test?
How long will I need to wait for results?
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