ANCA
Also known as: Anti-Neutrophil Cytoplasmic Antibodies
What Does ANCA Measure?
ANCA, or Anti-Neutrophil Cytoplasmic Antibodies, are autoantibodies that target proteins found in the cytoplasm of neutrophils (a type of white blood cell). The ANCA blood test detects the presence and pattern of these antibodies, most commonly identifying two main subtypes: c-ANCA (cytoplasmic pattern), which primarily targets a protein called proteinase 3 (PR3), and p-ANCA (perinuclear pattern), which mainly targets myeloperoxidase (MPO). The test uses indirect immunofluorescence to identify the staining pattern, and confirmatory ELISA or immunoassay testing is then used to identify the specific target antigen.
Why Does ANCA Matter?
ANCA testing is critically important for diagnosing a group of rare but serious autoimmune conditions collectively known as ANCA-associated vasculitides (AAV) — diseases characterized by inflammation and destruction of small blood vessels throughout the body. The most notable of these conditions include Granulomatosis with Polyangiitis (GPA, formerly Wegener's granulomatosis), Microscopic Polyangiitis (MPA), and Eosinophilic Granulomatosis with Polyangiitis (EGPA, formerly Churg-Strauss syndrome). These diseases can affect the kidneys, lungs, sinuses, skin, and nervous system and can be life-threatening if not diagnosed and treated promptly. ANCA levels can also help monitor disease activity and treatment response, making them a valuable tool in ongoing patient management.
Normal Ranges
Males
Negative (no ANCA detected); PR3-ANCA <2.8 U/mL, MPO-ANCA <3.5 U/mL (reference ranges vary by laboratory)
Females
Negative (no ANCA detected); PR3-ANCA <2.8 U/mL, MPO-ANCA <3.5 U/mL (reference ranges vary by laboratory)
Children
Negative (no ANCA detected); reference values similar to adults but vary by laboratory and assay used
Causes of High Levels
- Granulomatosis with Polyangiitis (GPA) — c-ANCA/PR3-ANCA positive in up to 90% of active generalized disease
- Microscopic Polyangiitis (MPA) — predominantly p-ANCA/MPO-ANCA positive
- Eosinophilic Granulomatosis with Polyangiitis (EGPA/Churg-Strauss syndrome)
- Drug-induced vasculitis or lupus-like syndrome (e.g., caused by hydralazine, propylthiouracil, minocycline)
- Inflammatory bowel disease (Crohn's disease and ulcerative colitis can produce atypical p-ANCA)
- Certain infections such as infective endocarditis, HIV, and some bacterial or fungal infections
Causes of Low Levels
- Disease remission following successful immunosuppressive therapy for AAV
- Early or limited-stage ANCA-associated vasculitis where antibody levels may be low or borderline
How to Improve Your ANCA
Diet
- Follow an anti-inflammatory diet rich in fruits, vegetables, whole grains, and omega-3 fatty acids to support immune regulation
- Increase consumption of fatty fish (salmon, mackerel, sardines — 2-3 servings per week) for their anti-inflammatory omega-3 content
- Reduce intake of ultra-processed foods, refined sugars, and trans fats, which promote systemic inflammation
- Ensure adequate vitamin D intake through fortified foods, fatty fish, and eggs, as deficiency is linked to autoimmune dysregulation
- Stay well-hydrated and limit alcohol consumption, especially when kidneys may be affected by vasculitis
Supplements
- Vitamin D3: 1,000–4,000 IU/day (consult a physician, particularly if levels are deficient, as it plays a role in immune modulation)
- Omega-3 fatty acids (fish oil): 2–4 g/day of combined EPA/DHA to help reduce inflammatory signaling
- Folic acid: 1–5 mg/day if prescribed methotrexate as part of vasculitis treatment, to reduce side effects
- Calcium: 1,000–1,200 mg/day in combination with vitamin D if on long-term corticosteroid therapy to protect bone density
- Probiotics: Multi-strain formulas (Lactobacillus, Bifidobacterium) to support gut microbiome and immune balance — consult a doctor before starting
Related Biomarkers
Frequently Asked Questions
What does a positive ANCA test mean?
A positive ANCA test means that your blood contains antibodies that attack proteins in your own neutrophils. This is a strong indicator of an autoimmune condition called ANCA-associated vasculitis (AAV), which causes inflammation of small blood vessels. The specific type — c-ANCA (targeting PR3) or p-ANCA (targeting MPO) — can help identify which vasculitis condition is present. However, a positive result should always be interpreted alongside symptoms and other tests, as false positives can occur with infections, medications, or other autoimmune diseases.
Can you have ANCA-associated vasculitis with a negative ANCA test?
Yes, this is possible. Approximately 10–30% of patients with ANCA-associated vasculitis, particularly those with limited or early-stage disease, may test ANCA-negative. This is sometimes called 'ANCA-negative vasculitis.' In such cases, diagnosis relies on clinical symptoms, imaging, and tissue biopsy. Negative ANCA results do not definitively rule out vasculitis, which is why a thorough clinical evaluation is essential.
How is ANCA-associated vasculitis treated?
Treatment for ANCA-associated vasculitis typically involves two phases: induction (to bring the disease into remission) and maintenance (to prevent relapse). Induction therapy usually includes high-dose corticosteroids (such as prednisone) combined with either rituximab (a biologic medication) or cyclophosphamide. Once remission is achieved, less intensive maintenance therapy with rituximab, azathioprine, or mycophenolate mofetil is used. Treatment must be supervised by a specialist, and ANCA levels are monitored over time to guide therapy adjustments.