MPO and purpura: MPO-ANCA should be tested with antigen-specific immunoassays in any patient with eosinophilic asthma and clinical features suggestive of EGPA (such as constitutional symptoms, purpura, polyneuropathy, unexplained heart, gastrointestinal or renal disease, and/or pulmonary infiltrates or hemorrhage) (152), however, only approximately one-third of patients are ANCA-positive (9).