The Myeloperoxidase (MPO) ANCA test detects autoantibodies against myeloperoxidase (MPO), which are associated with microscopic polyangiitis (MPA) and other forms of ANCA-associated vasculitis (AAV). It helps diagnose and monitor small-vessel vasculitis, which can cause kidney, lung, and nerve damage.
✅ Diagnose Microscopic Polyangiitis (MPA)
✅ Differentiate ANCA-associated vasculitis (MPA vs. GPA vs. EGPA)
✅ Assess risk of kidney disease and lung involvement
✅ Monitor disease activity and treatment response
| Result | Interpretation |
|---|---|
| Negative | No significant MPO antibodies detected (low likelihood of MPA) |
| Low Positive | May indicate mild inflammation or early disease, further evaluation needed |
| High Positive | Suggests microscopic polyangiitis (MPA), eosinophilic granulomatosis with polyangiitis (EGPA), or active vasculitis |
🔹 MPO-ANCA is strongly associated with MPA, but a negative test does not rule out disease.
🔹 Proteinase 3 (PR3) ANCA is also tested to differentiate GPA vs. MPA.
| ANCA Type | Fluorescence Pattern | Associated Disease |
|---|---|---|
| PR3-ANCA (c-ANCA) | Cytoplasmic (c-ANCA) | Granulomatosis with Polyangiitis (GPA, Wegener’s) |
| MPO-ANCA (p-ANCA) | Perinuclear (p-ANCA) | Microscopic Polyangiitis (MPA), Eosinophilic Granulomatosis with Polyangiitis (EGPA) |
| Atypical ANCA | Irregular staining | Seen in inflammatory bowel disease (IBD), infections |
🔹 Kidney involvement (glomerulonephritis) → Blood in urine, kidney failure
🔹 Lung inflammation → Cough, shortness of breath, lung scarring
🔹 Skin lesions → Purpura, ulcers, nodules
🔹 Nerve damage → Numbness, weakness (mononeuritis multiplex)
🔹 Fever, weight loss, joint pain
✔ PR3-ANCA (c-ANCA) → Helps differentiate MPA from GPA
✔ Inflammatory Markers (ESR, CRP) → Check for active inflammation
✔ Kidney Function Tests (Creatinine, Urinalysis) → Evaluate for vasculitis-related kidney damage
✔ Chest X-ray or CT Scan → Assess lung involvement
✔ Tissue Biopsy (Kidney, Lung, or Skin) → Confirms vasculitis diagnosis
🔹 Consult a rheumatologist or nephrologist for further evaluation.
🔹 Start immunosuppressive treatment (steroids, rituximab, cyclophosphamide) if active vasculitis is present.
🔹 Monitor regularly for disease flares or organ involvement.