From the Guidelines
ANCA blood tests are a crucial diagnostic tool for detecting anti-neutrophil cytoplasmic antibodies, which are associated with certain autoimmune diseases, and MPO (myeloperoxidase) is a specific target antigen associated with p-ANCA, with positive MPO-ANCA results commonly seen in microscopic polyangiitis and eosinophilic granulomatosis with polyangiitis, as recommended by the 2024 EULAR guidelines for the management of ANCA-associated vasculitis 1.
Key Points
- ANCA blood tests detect two main patterns: c-ANCA (cytoplasmic) and p-ANCA (perinuclear)
- MPO (myeloperoxidase) is a specific target antigen associated with p-ANCA
- Positive MPO-ANCA results are commonly seen in microscopic polyangiitis, eosinophilic granulomatosis with polyangiitis, and sometimes in renal-limited vasculitis
- Normal results show negative or low ANCA titers, while elevated levels suggest active autoimmune inflammation
- The interpretation of these results must be done by a healthcare provider who considers clinical symptoms alongside the test values
Diagnosis and Treatment
- ANCA tests are not definitive on their own and may require additional testing like tissue biopsies for diagnosis confirmation
- Treatment depends on the specific condition identified and may include immunosuppressants like cyclophosphamide, rituximab, or corticosteroids, as recommended by the 2021 American College of Rheumatology/Vasculitis Foundation guideline for the management of ANCA-associated vasculitis 1
- Regular monitoring of ANCA levels can help track disease activity and treatment effectiveness in diagnosed patients
Recommendations
- The 2024 EULAR guidelines recommend testing for both PR3-ANCA and MPO-ANCA using a high-quality antigen-specific assay as the primary method of testing 1
- The guidelines also recommend treatment with a combination of glucocorticoids and either rituximab or cyclophosphamide for induction of remission in patients with new-onset or relapsing GPA or MPA with organ-threatening or life-threatening disease 1
From the Research
ANCA Blood Test Results
- ANCA (Antineutrophil cytoplasmic antibody) blood tests are used to diagnose and monitor ANCA-associated vasculitis (AAV) [ 2 ].
- The test results can indicate the presence of specific types of ANCA, such as myeloperoxidase (MPO)-ANCA or proteinase 3 (PR3)-ANCA [ 3 ].
- MPO-ANCA is often associated with microscopic polyangiitis (MPA) and granulomatosis with polyangiitis (GPA), while PR3-ANCA is more commonly found in GPA [ 2 ].
MPO-ANCA Positive GPA
- MPO-ANCA positive GPA is a distinct subset of AAV, characterized by milder renal injury and a higher proportion of female patients [ 2 ].
- Patients with MPO-ANCA positive GPA tend to have less severe renal lesions and a lower risk of developing end-stage renal disease (ESRD) compared to those with MPO-ANCA positive MPA [ 2 ].
- MPO-ANCA positive GPA patients are more likely to experience relapse than those with MPO-ANCA positive MPA [ 2 ].
Clinical Characteristics and Treatment
- The clinical characteristics of MPO-ANCA positive GPA can vary, but often include ear, nose, and throat (ENT) involvement, nervous system involvement, and mild renal impairment [ 4 ].
- Treatment for MPO-ANCA positive GPA typically involves immunosuppressive therapy, such as glucocorticoids and cyclophosphamide or rituximab [ 3 ].
- The optimal treatment strategy may depend on the individual patient's characteristics and disease severity, and may involve a combination of induction and maintenance therapies [ 5 ].
Pathogenesis and Disease Mechanisms
- The pathogenesis of MPO-ANCA positive GPA is not fully understood, but is thought to involve the activation of neutrophils and the formation of immune complexes [ 3 ].
- Recent studies have shown that MPO-ANCA IgG can induce different forms of small vessel vasculitis based on the type of synergistic immune stimuli [ 6 ].
- Further research is needed to fully understand the disease mechanisms and to develop more effective treatments for MPO-ANCA positive GPA [ 6 ].