Clinical Information

Antineutrophil cytoplasmic antibodies (ANCA) can occur in patients with small blood vessel vasculitis, including granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA), or eosinophilic granulomatosis with polyangiitis (EGPA), collectively referred to as ANCA-associated vasculitis (AAV).(2) Detection of ANCA is a well-established diagnostic test for the evaluation of patients suspected of having AAV.(3) ANCA react with enzymes in the cytoplasmic granules of human neutrophils including proteinase 3 (PR3), myeloperoxidase (MPO), elastase, and cathepsin G amongst others. Of these, PR3-ANCA and MPO-ANCA are the best characterized in AAV. Antibodies to PR3-ANCA occur in patients with GPA and produce a characteristic pattern of granular cytoplasmic fluorescence on ethanol-fixed neutrophils called the cytoplasmic ANCA pattern. Antibodies to MPO-ANCA occur predominately in patients with MPA and produce a pattern of perinuclear cytoplasmic fluorescence on ethanol-fixed neutrophils called the perinuclear ANCA (pANCA) pattern.(4) EGPA may be pANCA positive with reactivity to MPO-ANCA or negative for ANCA. The pANCA pattern may also be observed in patients with inflammatory bowel disease, predominantly ulcerative colitis, usually in the absence of detectable MPO-ANCA reactivity.