ANCA-Associated Vasculitis Diagnosis and Management

Introduction to ANCA Testing

• The American College of Rheumatology recommends using a combination of antigen-specific immunoassays (ELISA) for proteinase-3 (PR3) and myeloperoxidase (MPO) for detecting ANCA-associated vasculitides (AAV) 1

ANCA Patterns and Clinical Significance

• c-ANCA (Cytoplasmic Pattern) with PR3 specificity is present in 80-90% of GPA patients with active systemic disease, confirming the diagnosis in up to 95% of cases 2
• c-ANCA with PR3 specificity has a specificity of 99% and sensitivity of 73% when using combined IIF and ELISA techniques 3, 4
• p-ANCA (Perinuclear Pattern) with MPO specificity is more common in MPA and EGPA, detected in 30-40% of EGPA patients 2, 6

Diagnostic Approach

• The European Renal Association recommends screening with antigen-specific ELISA for both MPO-ANCA and PR3-ANCA in suspected vasculitis cases 1
• Confirmatory IIF can be performed if ELISA is positive to assess pattern 3, 4

Monitoring and Prognosis

• Sequential c-ANCA monitoring can be useful in predicting relapse, though not all patients show classical fluctuation with disease activity 3, 4, 5, 6
• ANCA-positive patients tend to have more frequent relapses than ANCA-negative patients, requiring vigilant monitoring 6