Synonyms: c-ANCA, anti-PR3; p-ANCA, anti-MPO
Related tests: anti-PR3, anti-MPO
Clinical significance
Antineutrophil cytoplasmic antibodies (ANCA) are markers used in the diagnosis of systemic and localised vasculitis. ANCA are divided into two subclasses: c-ANCA, directed against proteinase 3 (anti-PR3) in the azurophilic granules of neutrophils, which give a cytoplasmic (c) pattern on indirect immunofluorescence, and p-ANCA, directed against myeloperoxidase (anti-MPO), with perinuclear (p) fluorescence. c-ANCA is more common in Wegener’s granulomatosis, while p-ANCA is found mainly in microscopic polyangiitis with sclerosing glomerulonephritis. In Churg-Strauss syndrome ANCA (both c and p) are present in 40-60% of cases.
Clinical indications
Systemic and localised vasculitis.
Sample type
The patient must have a blood sample taken.
Preparation
You must fast for at least 8 hours; a small amount of water is allowed. You must have been standing or sitting upright for at least 30 minutes.
Notes
If the immunofluorescence test is positive, anti-PR3 and anti-MPO must also be tested by ELISA for a correct clinical assessment. There are cases of positive ANCA with negative anti-PR3 and anti-MPO, also called atypical ANCA, found in inflammatory bowel disease (Crohn’s disease, ulcerative colitis), autoimmune hepatitis and cholangitis, SLE and rheumatoid arthritis.