What is the approach to a vasculitis workup?

Approach to Vasculitis Workup

The diagnostic workup for vasculitis requires a structured approach including clinical assessment, laboratory testing, imaging studies, and histopathological confirmation through biopsy, with biopsy remaining the gold standard for definitive diagnosis. 1

Initial Laboratory Evaluation

• Essential laboratory tests:

  • Complete blood count with differential
  • Inflammatory markers: ESR and CRP
  • Comprehensive metabolic panel including renal function (creatinine, GFR)
  • Urinalysis with microscopic examination and quantification of proteinuria
  • ANCA testing (both immunofluorescence and ELISA for PR3/MPO)
  • Complement levels (C3, C4)
  • Immunoglobulin levels
  • Hepatitis B and C serology

• ANCA testing specifics:

  • Must include both indirect immunofluorescence (cytoplasmic or perinuclear pattern) AND antigen-specific ELISA for PR3 and MPO 2
  • A positive ANCA alone is not diagnostic and must be interpreted in clinical context 1
  • About 90% of patients with small-vessel vasculitis have ANCA directed primarily to MPO or PR3 1

Biopsy - The Gold Standard

• Histopathological evidence remains the definitive diagnostic method for vasculitis 2
• Diagnostic yield of biopsies demonstrating either granuloma or vasculitis exceeds 70% 2
• Biopsy site selection:
  • Choose the most clinically involved accessible site 1
  • For suspected GCA: temporal artery biopsy (at least 1 cm length) 1
  • For ANCA-associated vasculitis: kidney, lung, skin, or nerve depending on involvement

Imaging Studies

• Selection based on suspected vessel size involvement:

  • Large vessel vasculitis: CT/CTA, MRI/MRA, or FDG-PET/CT 1
  • Medium vessel vasculitis: CTA of affected regions (renal, mesenteric, coronary) 1
  • Small vessel vasculitis: Focus on end-organ damage assessment

• Specific imaging recommendations:

  • MRI/MRA: Useful for assessing vessel wall inflammation without radiation exposure 1
  • FDG-PET/CT: Detects inflammatory cells in vessel walls, particularly useful for large vessel vasculitis 1
  • Renal involvement: Ultrasound as initial assessment

Disease-Specific Considerations

For ANCA-Associated Vasculitis

• Complete ANCA panel with immunofluorescence and ELISA for PR3/MPO 2
• Assess for multi-organ involvement: pulmonary, renal, ENT, skin, neurologic 2
• Renal function assessment with GFR using estimating equations (MDRD or Cockroft-Gault) 2
• Microscopic examination of urine and quantification of proteinuria 2

For Eosinophilic Granulomatosis with Polyangiitis (EGPA)

• Check for marked peripheral eosinophilia (>1500 cells/μl or >10%) 2
• Assess IgE levels
• Additional testing: toxocariasis, HIV, specific IgE and IgG for Aspergillus, tryptase and vitamin B12 2

For Cryoglobulinemic Vasculitis

• Cryoglobulin testing
• Hepatitis C testing (essential) 2

Disease Activity Monitoring

• Use validated assessment tools:

  • Birmingham Vasculitis Activity Score
  • Disease Extent Index
  • Vasculitis Damage Index
  • Short Form 36 2

• Regular monitoring of:

  • Inflammatory markers (ESR, CRP)
  • ANCA levels (in ANCA-associated vasculitis)
  • Renal function and urinalysis
  • Organ-specific tests based on involvement

Important Caveats

• Do not delay treatment in rapidly deteriorating patients with clinical presentation compatible with small-vessel vasculitis and positive MPO or PR3-ANCA while waiting for biopsy results 1

• Patients with vasculitis should be managed in collaboration with, or at centers of expertise 2, 1

• Serial ANCA measurements are particularly important in studies evaluating treatments that directly aim to reduce circulating ANCA levels 2

• Biomarkers must be interpreted in the context of clinical findings, as they are not specific in isolation 2