Antineutrophil cytoplasmic antibodies (ANCA): Role in disease pathogenesis, diagnosis, and monitoring ANCA associated vasculitis

Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a small-vessel vasculitis. The exact mechanism of ANCA involvement in the pathogenesis of AAV is not fully understood. It is an autoimmune disease with multifactorial pathophysiology. The most common ANCA target antigens are myeloperoxidase and proteinase 3. In addition to autoantibodies, dysregulated T and B cells have a pivotal pathophysiological role in this disease. Though the mechanism of action of ANCA is still being explored, ANCA serology is being increasingly used for classification of AAV, though the histological examination still remains the gold standard of diagnosis. The international consensus statement on reporting of ANCA recommended use of both IIF and ELISA as 5% of IIF negative results are ELISA positive. Though ANCA positivity increases the risk of recurrence four or more times, only a weak association is observed between ANCA and disease activity. Controversy exists regarding the utility of serial measurements of ANCA in patients with AAV to predict disease relapse. However, based upon current evidence the treatment decisions should not be based solely on the levels of ANCA titers in patients with AAV.