What labs are recommended to evaluate for vasculitis causing recurrent strokes?

Laboratory Evaluation for Vasculitis Causing Recurrent Strokes

A comprehensive laboratory workup for suspected vasculitis causing recurrent strokes should include erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), complete blood count, ANCA testing (both immunofluorescence and ELISA for PR3 and MPO), and cerebrospinal fluid analysis. 1, 2

First-Line Laboratory Tests

Inflammatory Markers

• ESR and CRP: Essential baseline inflammatory markers, though non-specific 2
• Complete blood count: To assess for anemia, leukocytosis, or eosinophilia (particularly important in certain vasculitides) 1, 2

Autoimmune Markers

• ANCA testing:
  • Both immunofluorescence (to detect cytoplasmic or perinuclear pattern) and ELISA (for PR3 and MPO specificity) 1, 2
  • The 2017 revised consensus recommends high-quality antigen-specific immunoassays as the preferred screening methodology 2
  • ANCA subtypes (PR3-ANCA and MPO-ANCA) correlate with different clinical presentations 2

Renal Function Assessment

• Serum creatinine: To evaluate renal involvement 1
• Urinalysis: For microscopic hematuria, proteinuria, and casts 1

Second-Line Laboratory Tests

Additional Autoimmune Markers

• Rheumatoid factor
• Antinuclear antibody (ANA)
• Anti-DNA antibody
• Anti-Ro/SSA and La/SSB antibodies
• Anti-glomerular basement membrane (GBM) antibodies 2, 3

Coagulation Studies

• Anticardiolipin antibody
• Lupus anticoagulant 3

Immunological Tests

• Complement levels (C3, C4, CH50)
• Immunoglobulin levels
• Cryoglobulins 2

Infectious Disease Screening

• Hepatitis B and C serology: Particularly important for polyarteritis nodosa and cryoglobulinemic vasculitis 1, 2
• HIV testing: Due to high coexistence with certain vasculitides 1
• Consider specific infectious agents: VZV, syphilis, tuberculosis based on clinical suspicion 1, 4

Cerebrospinal Fluid Analysis

• Cell count and differential: Look for lymphocytic pleocytosis
• Protein levels: Often elevated in CNS vasculitis
• Specific antibody testing: Anti-VZV IgG has highest sensitivity for VZV vasculitis 1

Important Considerations

1. Targeted screening approach: Evidence suggests that universal vasculitis screening in all young stroke patients has a low yield (only 2% positive in one study) 3. Testing should be guided by clinical suspicion based on:

   • Recurrent strokes despite standard therapy
   • Fever of unknown origin
   • Multifocal neurological events
   • Unexplained skin lesions
   • Glomerulopathy
   • Elevated inflammatory markers 1

2. Interpretation challenges: ESR and CRP are non-specific and don't distinguish between vasculitis activity and concurrent infection 2, 5

3. ANCA monitoring limitations: While ANCA antibodies may predict poor prognosis in some patients, their use in monitoring disease activity has minor importance 5

4. Common pitfall: Relying solely on laboratory tests without clinical correlation. The diagnosis of vasculitis requires integration of clinical, laboratory, and imaging findings 1

5. Expert consultation: Given the complexity of diagnosis, patients with suspected vasculitis should be managed in collaboration with centers of expertise 1

Remember that a definitive diagnosis often requires tissue biopsy showing typical features of vasculitis, though this may not always be feasible for CNS vasculitis 1.