This assay is useful for evaluating patients suspected of having autoimmune vasculitis, including both Wegeners granulomatosis and microscopic polyangiitis. 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). Positive results for ANCA demonstrate two main patterns: cytoplasmic (cANCA) and perinuclear (pANCA). These patterns are observed in a range of small vessel vasculitis conditions, all categorized under ANCA-associated vasculitis (AAV), which includes granulomatosis with polyangiitis, microscopic polyangiitis, and eosinophilic granulomatosis with polyangiitis.