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Diagnostic Tests – C-ANCA (Antineutrophil Cytoplasmic Antibody)
1. What is this?
C-ANCA is a serologic test used to diagnose granulomatosis with polyangiitis (GPA), formerly known as Wegener’s granulomatosis. It is the best initial test to make a specific diagnosis of this vasculitic disorder. The antibodies are directed against proteinase-3 (PR3) in neutrophils.
2. How is it done?
C-ANCA is a blood test analyzed using indirect immunofluorescence microscopy. The characteristic cytoplasmic (C-ANCA) staining pattern reflects antibodies targeting PR3, which is highly associated with granulomatosis with polyangiitis.
3. When do you answer C-ANCA?
You should select C-ANCA when a patient presents with a classic triad of involvement:
ENT symptoms + lung disease + renal findings → C-ANCA
4. What is the most accurate diagnostic test?
The most accurate (definitive) diagnostic test for granulomatosis with polyangiitis is a tissue biopsy, typically from:
1. What is this?
C-ANCA is a serologic test used to diagnose granulomatosis with polyangiitis (GPA), formerly known as Wegener’s granulomatosis. It is the best initial test to make a specific diagnosis of this vasculitic disorder. The antibodies are directed against proteinase-3 (PR3) in neutrophils.
2. How is it done?
C-ANCA is a blood test analyzed using indirect immunofluorescence microscopy. The characteristic cytoplasmic (C-ANCA) staining pattern reflects antibodies targeting PR3, which is highly associated with granulomatosis with polyangiitis.
3. When do you answer C-ANCA?
You should select C-ANCA when a patient presents with a classic triad of involvement:
- Upper respiratory tract disease: chronic sinusitis, otitis media
- Lower respiratory tract disease: cough, hemoptysis, sputum production, abnormal chest X-ray not responsive to antibiotics
- Renal disease: hematuria, red blood cell casts
ENT symptoms + lung disease + renal findings → C-ANCA
4. What is the most accurate diagnostic test?
The most accurate (definitive) diagnostic test for granulomatosis with polyangiitis is a tissue biopsy, typically from:
- Lung, or
- Kidney
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