Fig. 1

Identification of candidate biomarkers of disease activity in antineutrophil cytoplasmic antibody-associated vasculitis (AAV) using the selected reaction monitoring (SRM) assay. a Workflow for the development of SRM assays targeting marker candidates of disease activity in AAV. b Functional classification of marker candidates. c Comparison of 44 candidate markers discriminating between highly active AAV (before treatment) and remission (at 6 months after the start of treatment) using the SRM assay in protocol 1. Paired serum samples prepared from 23 patients (9 microscopic polyangiitis [MPA], 7 granulomatosis with polyangiitis [GPA], 5 eosinophilic granulomatosis with polyangiitis [EGPA], and 2 unclassifiable) were used in protocol 1. d Comparison of 15 candidate markers discriminating between highly active AAV and remission using the SRM assay in protocol 2. Paired serum samples prepared from 29 patients (10 MPA, 9 GPA, and 10 EGPA) were used in protocol 2. Volcano plots are used to look at fold changes and statistical significance simultaneously. Dot plots show − log₁₀ (p values) on the ordinate and log₂ (fold change values) on the abscissa for all activity marker candidates. The upper corners of the plot (red and blue dots) represent proteins that show both statistical significance and large fold changes. Red and blue dots indicate the proteins that were downregulated and upregulated after treatment, respectively. p Values were determined by Wilcoxon signed-rank test, and statistical significance was determined by < 0.05/44 or < 0.05/15 by Bonferroni correction. e Proteins downregulated after treatment with AUC scores > 0.7 in protocols 1 and 2. The upper six proteins were identified in protocol 1 and the lower three proteins in protocol 2. CRP C-reactive protein, ECM Extracellular matrix, LRG1 Leucine-rich alpha-2-glycoprotein 1, MMP9 Matrix metalloproteinase 9, TIMP1 Tissue inhibitor of metalloproteinase 1, TKT Transketolase, TNC Tenascin C