Diagnostic value of distinguishing and reporting different perinuclear ANCA (P-ANCA) immunofluorescence patterns: A prospective study

Abstract

Objectives: To investigate whether discriminating the classic perinuclear antineutrophil cytoplasmic antibody (P-ANCA) pattern from atypical P-ANCA and uninterpretable patterns improves the diagnostic utility of ANCA testing. Methods: All ANCA requests (n = 3,544) referred to Pathology Queensland were analyzed prospectively over 4 months for P-ANCA pattern subtypes and myeloperoxidase (MPO)-ANCA/PR3-ANCA results and correlated with clinical, laboratory, and radiologic evidence of necrotizing small vessel vasculitis. Results: Of the 436 perinuclear immunofluorescencepositive samples, 45 were classic P-ANCA, 163 were atypical P-ANCA, and 228 were antinuclear antibodies/ uninterpretable. The classic P-ANCA pattern had a significantly stronger association with vasculitis (30/45) than atypical P-ANCA (2/163) ( P