Positive ANCAs
April 24th, 2019
Overview
Anti-neutrophil cytoplasmic antibodies (ANCAs) are antibodies directed toward cytoplasmic granules of neutrophils and monocytes.
Assays
- Immunofluorescence (indirect) - measures distinctive cytoplasmic (c-ANCA) or perinuclear (p-ANCA) patterns that are not specific to a single antigen
- ELISA (direct) - measures PR3-ANCA and MPO-ANCA
ANCAs are positive in the presence of ANCA-associated small-vessel vasculitis, though may also be positive in other disease. As such, a high clinical suspicion should be present before ordering the test.
Interpretation
- c-ANCA (cytoplasmic) - directed against proteinase 3 (PR3) and several other moleculesStrongly associated with granulomatosis with polyangiitis (previously Wegener's granulomatosis)
- p-ANCA (peripheral) - directed against myeloperoxidase (MPO) and several other moleculesLess specific, but most strongly associated with microscopic polyangiitis
Causes of Positive ANCAs
ANCA-Associated Vasculitis
- Granulomatosis with polyangiitis (previously Wegener's granulomatosis)
- Microscopic polyangitis (MPA)
- Eosinophilic granulomatosis with polyangiitis (previously Churg-Strauss syndrome)
- Drug-induced vasculitis
Other
- Infective endocarditis
- Tuberculosis
- Primary sclerosing cholangitis (PSC)
- Pulmonary fibrosis
- Ulcerative colitis
- Rheumatoid arthritis
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