Work

048. Increased Sensitivity for Pr3-anca Using a Novel Chemiluminescence Immunoassay

Year: 2019

Type: article

Abstract: Background: ANCA-associated vasculitides (AAV) encompass granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA) and eosinophilic granulomatosis with polyangiitis (EGPA). In GPA, ANCA are mainly directed against proteinase 3 (PR3), while anti-myeloperoxidase (MPO) antibodies are primarily associated with MPA and EGPA. Sensitive and accurate PR3- and MPO-ANCA detection aids early diagnosis and might enable therapy monitoring in patients with AAV. The role of ANCA as biomarkers for monitoring disease activity is limited. This might depend, among other things, on the sensitivity, narrow measuring ranges and missing quantification of available assays. Novel immunoassays might reduce these limitations and add value to ANCA monitoring. Chemiluminescence immunoassays (ChLIA) and bead technology have lately become an interesting option for a fast, sensitive and accurate detection of PR3- and MPO-ANCA. Here, we investigated the diagnostic performance of a newly developed anti-PR3 ChLIA by comparison with a commercial ELISA. Methods: Sera from 209 clinically characterized AAV patients (101 GPA, 104 MPA, and 4 EGPA) and 112 disease controls were retrospectively analyzed with a novel anti-PR3 ChLIA which is based on human recombinant PR3 coated to magnetic beads. Samples were tested in parallel with an established anti- PR3 ELISA. Results: The anti-PR3 ChLIA showed a higher sensitivity for PR3-ANCA in AAV samples than the anti-PR3 ELISA, at slightly increased specificity (99% vs. 97%). Using ChLIA, the sensitivity for anti- PR3 rose from 86% to 90% in GPA and from 0% to 6% in MPA. The inter-assay concordance rates were 95% (GPA) and 98% (other AAV, disease controls). Conclusion: The novel anti-PR3 ChLIA outperformed the ELISA in both sensitivity and specificity, thus providing a valuable tool for AAV diagnosis and ANCA target antigen differentiation. Nevertheless, the clinical picture must not be ignored since it influences the therapy. Future studies with larger cohorts and using samples from AAV patients under treatment are necessary to further analyze the performance of the novel ChLIA and to study the relevance of PR3- ANCA level monitoring in follow-ups. Disclosures: Presenter is affiliated to the EUROIMMUN AG Abstract 048 Table 1.

Source: Lara D. Veeken

DOI: 10.1093/rheumatology/kez057.047