The ANCA test is a blood test used to detect autoimmune antibodies that target components within the cytoplasm of neutrophils (white blood cells). This test is specifically used in the diagnosis and monitoring of systemic vasculitis diseases such as Granulomatosis with Polyangiitis (GPA or Wegener’s disease), Microscopic Polyangiitis (MPA), and Eosinophilic Granulomatosis with Polyangiitis (EGPA or Churg-Strauss Syndrome).
Two main patterns are identified in the ANCA test:
c-ANCA (Cytoplasmic pattern): This is often associated with antibodies against Proteinase 3 (PR3).
p-ANCA (Perinuclear pattern): This is usually associated with antibodies against Myeloperoxidase (MPO).
A positive result on this test, especially when combined with clinical symptoms such as vasculitis, renal (kidney) issues, or pulmonary (lung) problems, can support the diagnosis of associated autoimmune diseases. However, a positive ANCA result may also be seen in other conditions, such as inflammatory bowel diseases or certain infections. Therefore, interpreting the results must be done alongside clinical evaluation and complementary tests (such as tissue biopsy).
This test is typically performed using Indirect Immunofluorescence (IIF) or Enzyme-Linked Immunosorbent Assay (ELISA) methods.
