PR3-ANCA and C-ANCA are related but not identical. PR3-ANCA refers to antibodies against proteinase‑3 (the specific antigen); C-ANCA describes a cytoplasmic staining pattern on indirect immunofluorescence. Most C-ANCA results reflect PR3-ANCA, and PR3-ANCA typically produces a C-ANCA pattern, but one term is antigen-specific and the other is a lab staining descriptor.

P-ANCA and C-ANCA are blood tests that detect antineutrophil cytoplasmic antibodies (ANCAs). C-ANCA usually targets proteinase‑3 (PR3) and is strongly associated with granulomatosis with polyangiitis. P-ANCA often targets myeloperoxidase (MPO) and is linked to microscopic polyangiitis, eosinophilic granulomatosis with polyangiitis, and some inflammatory or autoimmune conditions. They help diagnose and monitor small‑vessel vasculitis.

PR3‑ANCA is most strongly associated with granulomatosis with polyangiitis (GPA/Wegener’s). It can also be detected in other ANCA‑associated small‑vessel vasculitides (less commonly in microscopic polyangiitis and eosinophilic granulomatosis with polyangiitis), in some drug‑induced ANCA vasculitides, and occasionally with chronic infections or inflammatory conditions that provoke ANCA formation. Clinical correlation and further testing are required to confirm diagnosis.

PR3 stands for proteinase 3, a neutrophil serine protease stored in azurophilic granules that helps kill microbes and process proteins. It is the main autoantigen for PR3‑ANCA (c‑ANCA), an antibody linked to granulomatosis with polyangiitis. Blood tests for PR3 antibodies aid diagnosis and monitoring of ANCA‑associated vasculitis; elevated levels suggest active disease.

Wegener’s granulomatosis (granulomatosis with polyangiitis) is typically associated with c‑ANCA, most commonly anti‑proteinase 3 (PR3) antibodies. c‑ANCA/PR3 positivity is seen in about 80–90% of generalized cases, though some patients are ANCA‑negative or show p‑ANCA (anti‑MPO) less commonly. Definitive diagnosis combines serology with biopsy and imaging.

cANCA (cytoplasmic anti‑neutrophil cytoplasmic antibodies) is characteristically associated with granulomatosis with polyangiitis (GPA, formerly Wegener’s). cANCA typically targets proteinase‑3 (PR3) and strongly supports a GPA diagnosis when present, though it isn’t 100% specific; clinical correlation and further testing (imaging, biopsy) are required. Blood cANCA/PR3 levels can help monitor disease activity and treatment response.