MPO and rapidly progressive glomerulonephritis: In CS1, the serotypes of the 362 registered RPGN cases included 200 myeloperoxidase (MPO)-ANCA-positive, 98 anti-GBM-positive, and 9 proteinase-3 (PR3)-ANCA-positive cases, etc. CS2 included 96 of the MPO-ANCA-positive RPGN and 55 of the anti-GBM antibody-positive RPGN cases.