From the Guidelines
Laboratory tests for vasculitis should include complete blood count (CBC), erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), comprehensive metabolic panel, urinalysis, and specific autoantibody tests, such as antineutrophil cytoplasmic antibodies (ANCA) and anti-glomerular basement membrane antibodies, as recommended by the most recent guidelines 1.
Key Laboratory Tests
- Complete blood count (CBC) to check for anemia, leukocytosis, or thrombocytosis
- Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) to indicate inflammation
- Comprehensive metabolic panel to assess organ function
- Urinalysis to check for hematuria and proteinuria
- Autoantibody tests, including:
- Antineutrophil cytoplasmic antibodies (ANCA), with PR3-ANCA associated with granulomatosis with polyangiitis and MPO-ANCA with microscopic polyangiitis
- Anti-glomerular basement membrane antibodies for Goodpasture syndrome
- ANA, anti-dsDNA, and complement levels to evaluate lupus vasculitis
- Rheumatoid factor and anti-CCP antibodies to indicate rheumatoid vasculitis
- Cryoglobulins for cryoglobulinemic vasculitis
- Hepatitis B and C serologies, as they can trigger vasculitis
Importance of Tissue Biopsy
Tissue biopsy remains the gold standard for definitive diagnosis of vasculitis, as it provides histopathological evidence of vasculitis, such as pauci-immune glomerulonephritis or necrotising vasculitis in any organ 1. The diagnostic yield of biopsies varies depending on the organ targeted, with renal biopsy having a high diagnostic yield in patients with granulomatosis with polyangiitis (GPA) and renal involvement 1.
Clinical Context
These laboratory tests and tissue biopsy help determine the type of vasculitis, assess organ involvement, and guide treatment decisions, though results must be interpreted in the clinical context as no single test is diagnostic 1. A structured clinical assessment, including urine analysis and other basic laboratory tests, should be conducted at each clinical visit to detect new organ involvement, which may develop at any time in the disease course 1.
From the Research
Laboratory Tests for Vasculitis
The diagnosis of vasculitis involves various laboratory tests to provide useful information and help in distinguishing between different types of vasculitis. Some of the key laboratory tests include:
- Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) to assess inflammation levels 2
- Blood count, serum creatinine, and urinalysis to evaluate organ function and detect any abnormalities 2, 3
- Specific autoantibodies, such as anti-neutrophil cytoplasmic antibodies (ANCA), anti-glomerular basement membrane (GBM) antibodies, and anti-C1q antibodies, to diagnose specific types of vasculitis 2, 3, 4
- Complement and immunoglobulin levels to assess immune system function 2
- Cryoglobulin and Hepatitis B and C serology to detect any underlying infections or conditions 2, 3
Autoantibody Testing
Autoantibody testing, particularly ANCA testing, plays a crucial role in the diagnosis of vasculitis. The 2017 revised consensus recommendations on ANCA testing state that high-quality antigen-specific immunoassays are the preferred screening methodology for the diagnosis of ANCA-associated vasculitis 2. ANCA subtypes, such as proteinase-3-ANCA and myeloperoxidase-ANCA, are associated with different epidemiological, genetic, and clinical features 2.
Other Diagnostic Tools
In addition to laboratory tests, other diagnostic tools, such as angiographic studies and tissue biopsies, may be used to confirm the diagnosis of vasculitis. Angiography can help evaluate disease of large and medium-sized vessels, while tissue biopsies can provide a definitive diagnosis 3, 5. New imaging modalities are also becoming more useful in diagnosing vessel wall changes, particularly in large-vessel vasculitides 5.