From the Guidelines
The workup for vasculitis should include a combination of laboratory tests, imaging studies, and sometimes biopsies, with a focus on ANCA testing, including indirect immunofluorescence and ELISA, as recommended by the most recent guidelines 1. The initial laboratory tests should include:
- Complete blood count (CBC)
- Comprehensive metabolic panel
- Erythrocyte sedimentation rate (ESR)
- C-reactive protein (CRP) to assess for inflammation Specific autoantibody tests are crucial, including:
- Antineutrophil cytoplasmic antibodies (ANCA) with both proteinase-3 (PR3) and myeloperoxidase (MPO) specificity
- Antinuclear antibodies (ANA)
- Rheumatoid factor
- Anti-glomerular basement membrane antibodies
- Complement levels (C3, C4) Urinalysis should be performed to check for hematuria or proteinuria indicating kidney involvement. Additional tests may include:
- Hepatitis B and C serologies
- Cryoglobulins
- Serum immunoglobulins Imaging studies such as chest X-ray, CT scans, MRI, or angiography may be needed depending on suspected organ involvement. A tissue biopsy from an affected organ (skin, kidney, nerve, or temporal artery) often provides definitive diagnosis, as recommended by the guidelines 1. The choice of specific tests depends on the clinical presentation and suspected type of vasculitis, with the goal of establishing the diagnosis, determining disease extent, and guiding appropriate treatment. It is essential to note that the use of imaging modalities, such as ultrasound, MRI, CT, and PET, can be helpful in the diagnosis and monitoring of large vessel vasculitis, as recommended by the guidelines 1. However, the most recent guidelines for ANCA-associated vasculitis recommend biopsies to assist in establishing a new diagnosis and for further evaluation for patients suspected of having relapsing vasculitis 1.
From the Research
Vasculitis Workup Tests
- Serial measurements of acute phase reactants, complete blood cell count with differential, biochemistry profiles, urinalysis, and C3 and C4 levels should be obtained in all patients 2
- Antineutrophil cytoplasmic antibodies (ANCA) determination provides valuable information and is highly specific for the diagnosis of small-vessel vasculitides, particularly Wegener's granulomatosis and microscopic polyangiitis 2, 3
- Hepatitis-B and hepatitis-C testing is extremely useful, particularly in the presence of liver involvement and associated risk factors 2
- Angiographic studies may confirm the diagnosis, particularly if there is laboratory and clinical evidence of specific organ involvement 2
- A definite diagnosis is provided by a tissue biopsy, which should be performed whenever there is access to clinically affected tissue 2
Laboratory Tests for Vasculitis
- Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) are often helpful for the diagnosis of vasculitis, but are nonspecific and do not help in distinguishing between vasculitis disease activity and a concomitant infection or another source of inflammation 3
- Specific autoantibodies, such as anti-neutrophil cytoplasmic antibodies (ANCAs), anti-glomerular basement membrane (GBM) antibodies, and anti-C1q antibodies, are helpful for diagnosis 3
- High-quality antigen-specific immunoassays are the preferred screening methodology for the diagnosis of ANCA-associated vasculitis 3
Approach to Vasculitis Workup
- Determine the level of care the patient needs and order a basic laboratory evaluation while deciding on more specific laboratory tests to order 4
- Determine if the eruption represents vasculitis or vasculopathy, and rule out secondary causes such as infection, drug reactions, malignancy, and connective-tissue disorders 4
- Determine the size of the vessel involvement and the organ systems involved to narrow down the differential diagnosis 4
ANCA-Associated Vasculitis
- ANCA-associated vasculitis (AAV) represents a group of small vessel vasculitides characterized by granulomatous and neutrophilic tissue inflammation, often associated with the production of antibodies that target neutrophil antigens 5
- AAV can be classified into 3 categories based on patterns of clinical involvement: granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA), and eosinophilic GPA (EGPA) 5
- The prognosis of AAV has improved dramatically due to advances in the understanding of its pathogenesis and treatment modalities 5
Correlation of Laboratory Tests with Clinical Activity
- CRP, ESR, fibrinogen, d-dimers, albumin, and hemoglobin in the peripheral blood correlate well with the activity of vasculitis and identify severe patients 6
- Microscopic hematuria occurs in most patients with AAV and correlates with renal involvement, but does not correlate with disease severity 6
- Procalcitonin may be slightly increased in patients with active AAV without infection, but high concentrations are strongly associated with infectious complications 6