Anti-Neutrophil Cytoplasmic Antibodies (ANCA) Test
Anti-neutrophil cytoplasmic antibodies (ANCA) are autoantibodies that target antigenic structures within neutrophil cytoplasm (a type of white blood cell). They play a crucial role in the pathogenesis of vasculitis, a group of inflammatory diseases affecting blood vessels.
Types of ANCA and Their Detection
ANCA patterns can be distinguished using immunofluorescence microscopy:
- Perinuclear ANCA (p-ANCA): Fluorescence concentrates around the nucleus of neutrophils. These antibodies target myeloperoxidase (MPO).
- Cytoplasmic ANCA (c-ANCA): Fluorescence is distributed throughout the cytoplasm. These antibodies target proteinase 3 (PR3).
No special preparation is required.
Testing is recommended for patients with suspected vasculitis or related conditions, particularly if they experience:
- Unexplained pulmonary infiltrates
- Hemoptysis (coughing up blood)
- Kidney dysfunction
- Hematuria (blood in urine)
- Proteinuria (protein loss in urine)
- Nasal bleeding
- Peripheral polyneuropathy
A positive ANCA test may indicate:
Vasculitis-associated diseases:
- Granulomatosis with polyangiitis (GPA) (formerly Wegener’s disease) – primarily affects the lungs, kidneys, and sinuses.
- Microscopic polyangiitis (MPA) – may involve the lungs, kidneys, nervous system, and skin.
- Eosinophilic granulomatosis with polyangiitis (EGPA) (formerly Churg-Strauss syndrome) – often affects the skin and lungs and is commonly associated with asthma.
- Polyarteritis nodosa (PAN) – mainly affects the heart, kidneys, skin, and central nervous system.
- Necrotizing glomerulonephritis of unknown origin.
Other autoimmune or inflammatory conditions:
- Connective tissue diseases
- Autoimmune hepatitis
- Inflammatory bowel diseases (IBD)
- Certain types of cancer
Interpretation of Negative Results
A negative ANCA test generally suggests the absence of vasculitis or related autoimmune diseases. However, additional testing may be required for a definitive diagnosis.
This test is essential for diagnosing systemic vasculitis and autoimmune diseases, particularly when clinical symptoms suggest vascular inflammation.