Cytoplasmic Neutrophil Antibodies, Serum
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Antineutrophil cytoplasmic antibodies (ANCA) can occur in patients with autoimmune vasculitis including Wegener's granulomatosis (WG), microscopic polyangiitis (MPA), or organ-limited variants thereof such as pauci-immune necrotizing glomerulonephritis.(1) Detection of ANCA is a well-established diagnostic test for the evaluation of patients suspected of having autoimmune vasculitis. ANCA react with enzymes in the cytoplasmic granules of human neutrophils including proteinase 3 (PR3), myeloperoxidase (MPO), elastase, and cathepsin G. Antibodies to PR3 occur in patients with WG (both classical WG and WG with limited end-organ involvement) and produce a characteristic pattern of granular cytoplasmic fluorescence on ethanol-fixed neutrophils called the cANCA pattern. Antibodies to MPO occur predominately in patients with MPA and produce a pattern of perinuclear cytoplasmic fluorescence on ethanol-fixed neutrophils called the pANCA pattern.
Antineutrophil cytoplasmic antibodies (cANCA and pANCA):
-Evaluating patients suspected of having autoimmune vasculitis (both Wegener granulomatosis [WG] and microscopic polyangiitis)
-May be useful for monitoring treatment response in patients with WG (systemic or organ-limited disease); increasing titer suggests relapse of disease, while a decreasing titer suggests successful treatment
When used for diagnosis it is recommended that specific tests for proteinase 3 (PR3) ANCA and myeloperoxidase (MPO) ANCA be performed in addition to testing for cANCA and pANCA.(2) This panel of tests is available by ordering the VASC / Antineutrophil Cytoplasmic Antibodies Vasculitis Panel, Serum.
Positive results for antineutrophil cytoplasmic antibodies (cANCA or pANCA) are consistent with the diagnosis of Wegener granulomatosis (WG), either systemic WG with respiratory and renal involvement or limited WG with more restricted end-organ involvement. Positive results for pANCA are consistent with the diagnosis of autoimmune vasculitis including microscopic polyangiitis (MPA) or pauci-immune necrotizing glomerulonephritis. Sequential measurements of titers of cANCA may be useful to indicate the clinical course of patients with WG. Changes in titer of > or =2 serial dilutions are considered significant.(3) In patients with very low levels of cANCA, the immunofluorescent staining pattern may mimic the pANCA pattern. In patients with MPA, monitoring of disease activity may be performed by measuring MPO ANCA (MPO / Myeloperoxidase Antibodies, IgG, Serum).
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Current recommendations suggest that testing for antineutrophil cytoplasmic antibodies (ANCA) by immunofluorescence assay should not be relied upon exclusively to establish the diagnosis of Wegener's granulomatosis (WG) or microscopic polyangiitis (MPA) (see Interpretation).
Results for cANCA testing are titered if positive (1:4, 8, 16, 32, etc.). If positive for pANCA, results are reported as positive. Changes in titer of cANCA should not be relied upon exclusively to judge the disease activity of patients with WG or to determine the response to treatment. A decreasing titer of cANCA may lag behind the induction of clinical remission by several weeks in a patient with WG and, a detectable titer of cANCA may persist indefinitely despite induction of a stable clinical remission of disease. Conversely, a slight increase in the titer of cANCA should not be interpreted to mean an exacerbation of disease without further clinical and laboratory evidence of disease progression.
The presence of an antinuclear antibody may mimic a pANCA on ethanol-fixed neutrophils.
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
If positive for cANCA, results are titered.
Clinical References Provides recommendations for further in-depth reading of a clinical nature
1. Russell KA, Wiegert E, Schroeder DR, et al: Detection of anti-neutrophil cytoplasmic antibodies under actual clinical testing conditions. Clin Immunol 2002:103;196-203
2. Savige J, Gillis D, Benson E, et al: International consensus statement on testing and reporting of antineutrophil cytoplasmic antibodies (ANCA). Am J Clin Pathol 1999:111;507-513
3. Specks U, Homburger HA, DeRemee RA: Implications of cANCA testing for the classification of Wegener’s Granulomatosis: performance of different detection systems. Adv Exp Med Biol 1993:336;65-70