MPO and granulomatosis with polyangiitis: Antibody detection can be done by immunofluorescence (ANCA-P or ANCA-C) or by enzyme-linked immunoassay (Anti-MPO or Anti-PR3), the current recommendation being the last one due to reduced false positives.19,20 Anti-MPO has been observed to be more frequently associated with MPA (60%) and EGPA (up to 50%), unlike GPA with positive anti-PR3 around in 70% of cases21.