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Anti-Neutrophil Cytoplasmic Antibodies (ANCA)

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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.