What is the appropriate workup for a patient suspected of having vasculitis?

Appropriate Workup for Suspected Vasculitis

The appropriate workup for suspected vasculitis requires a comprehensive diagnostic approach including inflammatory markers, autoantibodies, laboratory studies, imaging based on vessel size, and biopsy of affected tissue, which remains the gold standard for definitive diagnosis. 1

Initial Laboratory Evaluation

• Essential inflammatory markers:

  • Erythrocyte sedimentation rate (ESR)
  • C-reactive protein (CRP)
  • Complete blood count with differential
  • Renal function tests (serum creatinine, estimated GFR)
  • Urinalysis with microscopic examination
  • Hepatitis B and C serology

• Autoantibody testing:

  • ANCA testing (both PR3-ANCA and MPO-ANCA) using high-quality antigen-specific assays
  • Anti-nuclear antibodies (ANA)
  • Cryoglobulins (if cryoglobulinemic vasculitis suspected)
  • Anti-phospholipase-A2-receptor antibodies (if membranous nephropathy suspected)

Imaging Studies Based on Suspected Vessel Size

• Large vessel vasculitis (Giant cell arteritis, Takayasu arteritis):

  • CT/CTA
  • MRI/MRA
  • FDG-PET/CT

• Medium vessel vasculitis (Polyarteritis nodosa):

  • CTA of affected regions (renal, mesenteric, coronary)

• Small vessel vasculitis (ANCA-associated vasculitis, IgA vasculitis):

  • MRI/MRA
  • FDG-PET/CT

Histopathological Confirmation

• Biopsy of affected tissue - gold standard for diagnosis with high diagnostic yield (up to 91.5% in GPA with renal involvement) 1
• Target the most accessible affected organ with highest diagnostic yield
• Common biopsy sites:
  • Skin (for palpable purpura)
  • Kidney (for glomerulonephritis)
  • Lung (for pulmonary infiltrates)
  • Nasal mucosa (for upper respiratory involvement)
  • Nerve (for mononeuritis multiplex)

Disease Activity Assessment

• Use validated assessment tools like Birmingham Vasculitis Activity Score (BVAS) for structured clinical examination 1
• Categorize patients according to disease severity to guide treatment decisions

Common Pitfalls and Caveats

1. Relying solely on ANCA testing - While useful for ANCA-associated vasculitis, structured clinical assessment should guide decisions rather than ANCA testing alone 1

2. Delaying biopsy - Early biopsy before starting treatment provides highest diagnostic yield; treatment may obscure histopathological findings

3. Inadequate tissue sampling - Ensure adequate tissue volume and proper handling for histopathology

4. Missing underlying causes - Always screen for:

   • Infections (particularly hepatitis B and C)
   • Malignancies
   • Medications that can trigger vasculitis

5. Failing to monitor for complications - Regular monitoring for treatment complications, particularly infections, is crucial 1

Special Considerations for ANCA-Associated Vasculitis

For suspected granulomatosis with polyangiitis (GPA) or microscopic polyangiitis (MPA), early diagnosis and treatment are essential for improving survival 1. The diagnostic workup should include:

• Both PR3-ANCA and MPO-ANCA testing using high-quality antigen-specific assays
• Assessment using the Birmingham Vasculitis Activity Score (BVAS/GPA)
• Evaluation for organ involvement, particularly renal, pulmonary, and upper respiratory tract

For complex cases or refractory disease, referral to centers of expertise is strongly recommended by both the European League Against Rheumatism and the American College of Rheumatology 1.