Clinical Information

Current recommendations suggest that testing for antineutrophil cytoplasmic antibodies (ANCA) by indirect immunofluorescence assay should not be relied upon exclusively to establish the diagnosis of granulomatosis with polyangiitis (GPA), microscopic polyangiitis, or eosinophilic granulomatosis with polyangiitis. Due to their lack of diagnostic specificities, all positive ANCA results must be confirmed using solid-phase immunoassays using proteinase 3-ANCA for cytoplasmic ANCA (cANCA) and myeloperoxidase-ANCA for perinuclear ANCA. Changes in titer of cANCA should not be relied upon exclusively to either judge the disease activity of patients with GPA or 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 GPA, 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.