Anti-neutrophil Cytoplasmic Antibody (ANCA)
Last updated: November 3, 2014
Synonyms: Cytoplasmic ANCA (C-ANCA), perinuclear ANCA (P-ANCA), myeloperoxidase (MPO), proteinase-3 (PR3) antibodies.
CPT Codes: ANCA screen 86255; ANCA titer (if screen positive) 86256; PR3 83520; MPO 83876 ; PR3 83520.
Description: ANCA test comprises a group of antibodies that bind to enzymes present in the cytoplasm of neutrophils. ANCAs are found in patients with several types of vasculitis and other autoimmune conditions, but most notably in granulomatosus with polyangiitis. ANCA testing is of greater diagnostic than prognostic value.
Method: ANCAs are assayed either by either indirect immunofluorescence (IIF) or using antigen specific immunoassays. IIF are performed using human neutrophils (or monocytes) fixed on a glass slide. Patient serum is added to the slide, and the presence and quantity of antibodies binding to the cellular cytoplasm is ascertained. Antigens detected by ANCA are cytoplasmic in location. Owing to an artifact that occurs during fixation of slides with ethanol, distinct cytoplasmic staining patterns are observed (see Table). With C-ANCA, a granular, diffuse, cytoplasmic staining pattern is observed. By contrast, P-ANCA exhibits perinuclear staining. An atypical perinuclear pattern, sometimes referred to as A-ANCA or X-ANCA, may also be observed. The different staining patterns are associated with binding to different antigens. Hence C-ANCA, P-ANCA and atypical ANCA staining patterns are best identified by IIF. Antibodies against proteinase 3 (PR3) and myeloperoxidase (MPO) antigen are easily assessed using specific immunometric assays.
Abnormal Results
C-ANCA: The antigen responsible for the C-ANCA pattern is proteinase-3; antibody testing specifically for this enzyme is another method of confirming a C-ANCA. Positive C-ANCA is associated with granulomatosus with polyangiitis (GPA; previously known as Wegener ’s granulomatosis), particularly in patients with active disease. Depending on the extent and activity of disease, C-ANCA has approximately a 50% to 90% sensitivity for GPA. Moreover, although C-ANCA may be seen rarely in other vasculitides (e.g., Churg-Strauss vasculitis, microscopic polyangiitis or idiopathic necrotizing and crescentic glomerulonephritis), it is relatively specific for GPA, with a specificity >90%. In very few GPA patients will the titer of C-ANCA correlate with disease activity. In addition to being a diagnostic marker, C-ANCA may play an etiopathogenic role in GPA as well.
P-ANCA: P-ANCA is associated with binding to various enzymes, including myeloperoxidase, lactoferrin, cathepsin, elastase, and others. P-ANCA and particularly myeloperoxidase antibodies are seen in approximately 60% of patients with microscopic polyarteritis and Churg-Strauss syndrome. P-ANCA may also be observed in a variety of other conditions, including inflammatory bowel disease, polyarteritis, and idiopathic crescentic glomerulonephritis.
| Table: Antineutrophil Cytoplasmic Antibodies | ||||
| Staining Pattern | Target Antigen | Clinical Association | ||
|---|---|---|---|---|
| C-ANCA | Granular, diffuse cytoplasmic | Proteinase-3 | Granulomatosus with polyangiitis (GPA or Wegener’s granulomatosis) | |
| P-ANCA | Perinuclear | MPO, lactoferrin, elastase, cathepsin, other antigens | Microscopic PAN, Churg-Strauss syndrome, idiopathic crescentic GN, inflammatory bowel disease, Felty’s syndrome, autoimmune hepatitis | |
| A-ANCA or X-ANCA | Atypical perinuclear | Unknown | HIV, endocarditis, inflammatory bowel disease | |
| C-ANCA, cytoplasmic antineutrophil cytoplasmic antibody; P-ANCA, perinuclear antineutrophil cytoplasmic antibody; MPO, myeloperoxidase; PAN, polyarteritis nodosa; GN, glomerulonephritis, HIV, human immuno- deficiency virus. | ||||
Indications: A serum ANCA test should be considered in the evaluation of patients with suspected granulomatosis with polyangiitis (also known as Wegener’s granulomatosis), microscopic polyangiitis (MPA), eosinophilic granulomatosis with polyangiitis (EGPA), an undiagnosed pulmonary-renal syndrome or systemic vasculitis. A positive ANCA assay has a sensitivity of 90% for GPA or MPA, but a lower specificity and should not avert the need for tissue biopsy or angiography to firmly establish a diagnosis of GPA or MPA. Serial ANCA testing is unlikely to correlated with disease activity or response to therapy over time.
Cost: ANCA screen, $220–260; individual tests for PR3, MPO or elastase antibodies range from $10–220.
BIBLIOGRAPHY
Tervaert JW, Heeringa P. Pathophysiology of ANCA-associated vasculitides: are ANCA really pathogenic? Neth J Med 2003;61:404–407. PMID: 15025415
Wiik A. Autoantibodies in vasculitis. Arthritis Res Ther 2003;5:147–152. PMID:12723981
Sinico RA, Radice A. Antineutrophil cytoplasmic antibodies (ANCA) testing: detection methods and clinical application. Clin Exp Rheumatol. 2014; 32 (3 Suppl 82):S112-7. PMID: 24854381
