PR3 (c-ANCA)

PR3 (c-ANCA) measures the autoantibodies (Cytoplasmic-Antineutrophil Cytoplasmic Antibodies or C-ANCA) related to a protein called proteinase 3 (PR3). This test helps diagnose and monitor autoimmune diseases such as granulomatosis with polyangiitis (GPA) and microscopic polyangiitis (MPA). A decrease in C-ANCA levels may suggest that the treatment is working. Therefore, this test helps evaluate treatment response in people with GPA or MPA. It may also be used to differentiate other conditions with similar symptoms, like infections or other autoimmune diseases. You may get tested if you experience symptoms like persistent coughing, difficulty breathing, chest pain, nosebleeds, skin rashes, sores, lumps, joint pain or swelling, fatigue, fever, and weight loss. C-ANCA test can help identify patients who may require closer monitoring or specifically guided treatment.