What laboratory tests should be ordered for a 33-year-old female with suspected vasculitis?

Laboratory Tests for Suspected Vasculitis in a 33-Year-Old Female

For a 33-year-old female with suspected vasculitis, the essential laboratory workup should include autoimmune serologies (ANCA, ANA, anti-GBM antibodies), complete blood count, inflammatory markers, renal function tests, and urinalysis. 1, 2

Initial Laboratory Evaluation

• Complete blood count with differential - to assess for anemia, leukocytosis, eosinophilia, or thrombocytosis 2, 3
• Inflammatory markers - Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) to evaluate degree of inflammation 2, 3
• Comprehensive metabolic panel - including renal function (creatinine, BUN) and liver function tests 2, 4
• Urinalysis - to detect hematuria, proteinuria, and red cell casts that suggest renal involvement 1

Autoimmune Serologies

• ANCA testing - using both indirect immunofluorescence (IIF) and enzyme-linked immunosorbent assays (ELISA) for:

  • Anti-PR3 (proteinase 3) antibodies - associated with granulomatosis with polyangiitis (GPA) 1, 4
  • Anti-MPO (myeloperoxidase) antibodies - associated with microscopic polyangiitis (MPA) and eosinophilic granulomatosis with polyangiitis (EGPA) 1, 3

• Anti-nuclear antibodies (ANA) - to evaluate for potential connective tissue diseases 1, 2

• Anti-glomerular basement membrane (GBM) antibodies - to rule out anti-GBM disease 1, 3

• Complement levels (C3, C4) - to assess for immune complex-mediated vasculitis 3

Additional Testing Based on Clinical Presentation

• Hepatitis B and C serology - particularly important if cryoglobulinemic vasculitis is suspected 2, 3
• Immunoglobulin levels - to evaluate for potential immunodeficiency or IgG4-related disease 1, 3
• Cryoglobulins - if cryoglobulinemic vasculitis is suspected 3
• Rheumatoid factor - may be elevated in rheumatoid vasculitis 4

Specific Considerations for Suspected Organ Involvement

• For suspected renal involvement: 24-hour urine collection for protein and creatinine clearance 1
• For suspected pulmonary involvement: Pulmonary function tests and diffusion capacity 5
• For suspected ENT involvement: Consider specific evaluation for granulomatosis with polyangiitis 1

Imaging Studies

• Chest imaging (X-ray or CT) - to evaluate for pulmonary involvement, granulomas, infiltrates, or cavitary lesions 1, 2
• Consider appropriate vascular imaging based on suspected vessel size involvement:
  • Large vessel: MRA, CTA, or PET-CT 2
  • Medium vessel: Conventional angiography 2, 6
  • Small vessel: Generally not visualized on imaging; tissue biopsy is preferred 2

Tissue Biopsy

• Kidney biopsy - provides definitive diagnosis and prognostic information in suspected renal vasculitis 1
• Skin biopsy - if cutaneous manifestations are present 7
• Other tissue biopsies - directed at clinically involved organs 1, 8

Important Considerations

• Do not delay treatment if clinical presentation is compatible with small-vessel vasculitis and MPO or PR3-ANCA serology is positive, especially in rapidly deteriorating patients 1
• Patients with suspected vasculitis should be managed in close collaboration with centers experienced in vasculitis management 1
• About 10% of patients with clinical features of ANCA-associated vasculitis may be ANCA-negative, requiring tissue biopsy for definitive diagnosis 1
• Consider alternative diagnoses in ANCA-negative cases, including systemic lupus erythematosus, infections, and malignancies 1, 7

Remember that early diagnosis and treatment are essential to reduce morbidity and mortality in vasculitis, making a comprehensive laboratory evaluation crucial for proper management 4.