MPO and anti-neutrophil cytoplasmic antibody-associated vasculitis: c-ANCA were detected in 21 (77.8%) and p-ANCA in 6 ANCA positive AAV patients (22.2%) and specificity of ANCA was PR3 directed in 15 (83.3%) and MPO directed in 3 (16.7%) of the 18 ANCA positive patients tested for PR3 / MPO specificity.