MPO and anti-neutrophil cytoplasmic antibody-associated vasculitis: • Use high-quality immunoassays (both MPO- and PR3-ANCA) is recommended as the first screening method for detection of ANCA in patients suspected of AAV • If the result is negative and there is a high clinical suspicion of AAV, include a distinct antigen-specific immunoassay (or IIF) to increase sensitivity • If the result is low-positive, confirm the result with a distinct antigen-specific immunoassay (or IIF) to increase specificity