PRTN3 and microscopic polyangiitis: The fact that the presence of PR3-ANCA in GPA and MPO-ANCA in MPA is endowed with the highest number of points (5 and 6, respectively), whereas positive MPO-ANCA in GPA and positive PR3-ANCA in MPA each result in one negative point attests to the crucial role of these antibodies in diagnosing GPA and MPA.