Prevalence and spectrum of rheumatic diseases associated with proteinase 3‐antineutrophil cytoplasmic antibodies (ANCA) and myeloperoxidase‐ANCA

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Abstract
Objectives. To evaluate the prevalence and association of antineutrophil cytoplasmic antibodies (ANCA) and their subtypes [proteinase 3 (PR3)‐ANCA, myeloperoxidase (MPO)‐ANCA] with distinct clinical features in various clinicopathological syndromes. Methods. All consecutive ANCA‐positive patients seen at the combined unit for rheumatology for Bad Bramstedt and the University of Lübeck between 1989 and 1999 were analysed. ANCA were detected by an immunofluorescence technique and ANCA subspecificities were determined by ELISA. Clinical features at presentation and diagnoses were recorded according to standardized procedures. Results. Among 4620 patients tested, 333 were cytoplasmic ANCA‐positive and 291 were perinuclear ANCA‐positive. cANCA/PR3‐ANCA were strongly associated with Wegener's granulomatosis (WG), whereas pANCA/MPO‐ANCA were associated with a diverse disease spectrum. Further investigation of PR3‐ANCA‐positive (n=80) and MPO‐ANCA‐positive patients (n=40) revealed a greater extent of disease [disease extent index (DEI); median 8 vs 5, Pvs 8) and had a lower frequency of peripheral neuropathy. Conclusions. ANCA testing is useful due to its high sensitivity and specificity, especially for cANCA/PR3‐ANCA in WG. We found a divergence in the disease spectrum between PR3‐ and MPO‐ANCA‐positive patients, characterized by higher DEI and extrarenal manifestations in the PR3‐ANCA group. MPO‐ANCA was rarely found in WG and was associated with less organ involvement.