Determination of ANCAs can aid in the diagnosis, but positivity is not conclusive and negative ANCAs are not sufficient to reject the diagnosis. Cytoplasmic staining ANCAs that react with the enzyme proteinase 3 (cANCA) in neutrophils (a type of white blood cell) are associated with<unk>  with polyangiitis. If the patient has renal failure or cutaneous vasculitis, these are the most logical organs to obtain a biopsy from. Rarely, thoracoscopic lung biopsy is required.
Granulomatosis with polyangiitis diagnostic study of choice
Microscopic polyangiitis differential diagnosis
Polyarteritis nodosa other diagnostic studies
Granulomatosis with polyangiitis differential diagnosis
Polyarteritis nodosa other imaging findings
Goodpasture syndrome other diagnostic studies
Microscopic polyangiitis echocardiography or ultrasound
Membranoproliferative glomerulonephritis diagnostic study of choice