What is the initial workup for a query of vasculitis?

Initial Workup for Query Vasculitis

The initial workup for suspected vasculitis should include ANCA testing (both immunofluorescence and ELISA), a biopsy of the affected tissue, structured clinical assessment, urinalysis, and basic laboratory tests to establish diagnosis and assess disease extent. 1

Diagnostic Approach

Clinical Assessment

• Perform a thorough clinical examination of the arterial tree 1
• Document organ involvement systematically using structured assessment tools 1
• Evaluate for specific symptoms based on suspected vasculitis type:
  • Small/medium vessel: purpura, skin lesions, peripheral neuropathy, glomerulonephritis
  • Large vessel: temporal artery tenderness, vascular bruits, pulse deficits, limb claudication

Laboratory Testing

Essential First-line Tests

1. ANCA testing 1

   • Indirect immunofluorescence (to detect cytoplasmic or perinuclear patterns)
   • ELISA for specific antigens (PR3 and MPO)
   • Note: A negative ANCA does not rule out vasculitis, particularly in certain subtypes

2. Basic laboratory panel

   • Complete blood count with differential
   • Comprehensive metabolic panel
   • Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP)
   • Urinalysis with microscopy 1
   • Complement levels (C3, C4) 2

3. Additional serologic testing

   • Hepatitis B and C screening (particularly with liver involvement) 2
   • Cryoglobulins 3
   • Circulating immune complexes 3
   • Autoantibody panel for collagen vascular diseases 3

Tissue Biopsy

• Biopsy of affected tissue is the gold standard for diagnosis 1

  • For temporal arteritis: temporal artery biopsy (at least 1 cm sample) 1
  • For cutaneous vasculitis: biopsy from most tender, reddish or purpuric lesion extending to subcutis 4
  • For ANCA-associated vasculitis: consider renal, lung, or nasal tissue biopsy

• Consider direct immunofluorescence on biopsy specimen to distinguish IgA-associated vasculitis (Henoch-Schönlein purpura) from IgG/IgM-associated vasculitis 4

Imaging Studies

• For large vessel vasculitis:

  • Magnetic resonance angiography (MRA)
  • Positron emission tomography (PET)
  • Conventional angiography when other modalities unavailable 1

• For ANCA-associated vasculitis:

  • Chest CT scan (for pulmonary involvement)
  • Sinus CT (for upper respiratory tract involvement) 1

Special Considerations

Disease-Specific Workup

For ANCA-Associated Vasculitis

• Test for both PR3-ANCA and MPO-ANCA 1
• Assess for organ involvement: renal, pulmonary, ENT, neurological
• Consider additional testing for differential diagnosis:
  • Toxocariasis serology
  • HIV testing
  • Aspergillus-specific IgE and IgG
  • Tryptase and vitamin B12 levels 1

For Giant Cell Arteritis

• Temporal artery biopsy should be performed but should not delay treatment if clinical suspicion is high 1
• Treatment with high-dose glucocorticoids should be initiated promptly if GCA is strongly suspected, especially with visual symptoms 1

Common Pitfalls to Avoid

1. Delaying treatment while awaiting biopsy results in cases with high clinical suspicion and risk of permanent organ damage
2. Relying solely on ANCA testing (false negatives occur, particularly in limited forms of disease)
3. Failing to exclude vasculitis mimics (thrombotic disorders, antiphospholipid syndrome) 4
4. Inadequate biopsy sampling (too small or from inappropriate site)
5. Not considering secondary causes of vasculitis (drugs, infections, malignancy, connective tissue diseases) 4, 3

By following this structured approach to the workup of suspected vasculitis, clinicians can establish a timely diagnosis, assess disease extent, and initiate appropriate treatment to prevent morbidity and mortality associated with these complex disorders.