AB0637 The role of antineutrophil cytoplasmic antibody (ANCA) in assessment of disease activity in systemic vasculitis

Abstract

BackgroundDespite the proven diagnostic significance, the prognostic role of ANCA, in particular for assessing disease activity, remains questionable. Numerous studies have attempted to estimate the role of ANCA monitoring with different results and a lack of consensus on reported outcomes [1].ObjectivesTo analyze the relationship between ANCA level and clinical or laboratory parameters of disease activity.MethodsThis is a retrospective analysis of 38 patients with ANCA-associated vasculitis (granulomatosis with polyangiitis – 25 patients, microscopic polyangiitis – 6 patients and eosinophilic granulomatosis with polyangiitis – 7 patients) from a single center observed from 2015 till the end of 2020. The diagnosis of ANCA-associated vasculitis was performed according to the ACR 1990 criteria or the Chapel Hill Consensus Conference 2012 nomenclature. The study included 20 women (52.6%) and 18 men (47.4%). The average age of patients was 49 (27-62) years, the mean duration of the disease was 26 (6-120) months. The clinical data, initial Birmingham vasculitis activity score (BVAS), erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), ANCA (ELISA test) against proteinase-3 (PR-3) and myeloperoxidase (MPO) were evaluated. Spearman's correlation analysis was used to investigate the relationship between ANCA levels and ESR, CRP levels, BVAS activity index. The diagnostic value of ANCA in determining the active disease was evaluated by ROC analysis with an estimation of the area under the ROC curve (AUC). The definition of active disease included new, persistent, or worsening clinical signs and/or symptoms attributed to GPA, MPA, or EGPA and not related to prior damage [2].ResultsPositivity for MPO-ANCA was observed in 23.7% of patients, and for PR3-ANCA - in 76.3% of patients. The BVAS activity index averaged 16 (IQR-13) points. The mean CRP level was 47.9 (IQR-90.0) mg/L and the ESR level was 30.1 (IQR-33.5) mm/h. There was a positive correlation between the level of both ANCA and the BVAS index (r = 0.43; 95% CI 0.11-0.66; p <0.01), as well as the level of ESR (r = 0.37; 95% CI 0.05-0.63; p <0.05). No relationship was found between CRP level and ANCA level (r = 0.22; 95% CI -0.15-0.54; p> 0.05), but a positive correlation was observed between CRP level and index BVAS activity (r = 0.41; 95% CI 0.05-0.67; p <0.05). When using ROC-analysis to determine the value of ANCA in the assessment of active disease, it was found that the AUC is 0.93 ± 0.04 (95% CI 0.84-1.01; p <0.01), which indicates excellent ability ANCA diagnose patients with active disease (sensitivity - 87.9%, specificity - 80.0%).ConclusionThe level of ANCA in patients with ANCA-associated vasculitis correlates with the Birmingham vasculitis activity score, as well as with the level of ESR. Determination of ANCA level can be used not only to diagnose ANCA-associated vasculitis, but also to assess disease activity.