Comprehensive Workup for Vasculitis
The appropriate workup for vasculitis requires a structured diagnostic approach based on vessel size classification (large, medium, or small vessel) and includes targeted laboratory testing, imaging studies, and often tissue biopsy for definitive diagnosis. 1
Classification and Initial Assessment
- Vasculitis is categorized based on vessel size involvement: large vessel vasculitis (LVV), medium vessel vasculitis (MVV), small vessel vasculitis, and variable vessel vasculitis 1
- Large vessels include the aorta and its main branches; medium vessels are main visceral arteries and initial branches; small vessels are intraparenchymal vessels and analog veins 1
- Initial laboratory evaluation should include complete blood count, comprehensive metabolic panel, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and urinalysis 2
- Anti-neutrophil cytoplasmic antibody (ANCA) testing should be performed using both indirect immunofluorescence and ELISA in suspected vasculitis cases 2
Imaging Studies by Vessel Size
Large Vessel Vasculitis (GCA and Takayasu Arteritis)
For Giant Cell Arteritis (GCA):
- Temporal artery biopsy should be performed whenever GCA is suspected (though treatment should not be delayed) 1
- Ultrasound of the temporal artery shows 88% sensitivity and 97% specificity for diagnosing temporal arteritis 1
- MRI/MRA of the head and neck can identify involvement of extracranial large arteries in large-vessel GCA (LV-GCA) 1
- FDG-PET/CT is valuable for diagnosis, showing inflammatory cell accumulation in vessel walls 1
For Takayasu Arteritis:
Medium Vessel Vasculitis (PAN and Kawasaki Disease)
For Polyarteritis Nodosa (PAN):
For Kawasaki Disease:
Small Vessel Vasculitis
- Tissue biopsy from the affected organ is the gold standard for diagnosis 3
- For cutaneous vasculitis, biopsy should be taken from the most tender, reddish, or purpuric lesional skin 3
- Concomitant biopsy for direct immunofluorescence helps distinguish IgA-associated vasculitis (Henoch-Schönlein purpura) from IgG/IgM-associated vasculitis 3
Cerebral Vasculitis Considerations
- MRI brain is the preferred initial imaging modality for suspected CNS vasculitis, with abnormal findings in >90% of cases 2
- Cerebrospinal fluid analysis may reveal increased opening pressure, elevated protein, or lymphocytic pleocytosis 2
- Cerebral arteriography (DSA) has been the standard imaging technique due to its submillimeter resolution 2
- Brain biopsy (cortical-leptomeningeal) is the most specific diagnostic test for diffuse or multifocal CNS vasculitis 2
Advanced Imaging Protocols
- FDG-PET/CT should be performed after 6 hours of fasting, with some studies suggesting 120-180 minute delay after injection for higher diagnostic accuracy 1
- MRI/MRA sequences should include:
- T2-weighted fast spin-echo or inversion recovery sequences
- ECG-gated rapid 3-D T1-weighted spoiled gradient-echo pulse sequences
- Post-contrast T1-weighted imaging with fat suppression 1
Follow-up Assessment
- In case of suspected relapse, ultrasound, FDG-PET, or MRI may be considered, particularly when laboratory markers are unreliable 1
- Imaging is not routinely recommended for patients in clinical and biochemical remission 1
- For patients treated with IL-6 pathway blockers (tocilizumab), imaging may be more valuable as ESR and CRP are not clinically informative 1
Common Pitfalls to Avoid
- Cerebral angiography has low specificity for vasculitis given overlap with other cerebrovascular diseases 2
- Not all individuals with vasculitis have clinical or laboratory signs of inflammation 2
- "Blind" treatment with immunosuppressive agents should be strictly avoided before establishing a definitive diagnosis 4
- Failing to distinguish between vasculitis and vasculitis-like syndromes (pseudovasculitis) such as thrombotic disorders 3
By following this structured approach to vasculitis workup, clinicians can establish an accurate diagnosis and initiate appropriate treatment to prevent irreversible organ damage and improve patient outcomes.