The Clinical Utility of Serum Alpha-1-Acid Glycoprotein in Reflecting the Cross-Sectional Activity of Antineutrophil Cytoplasmic Antibody-Associated Vasculitis: A Single-Centre Retrospective Study

Background and Objectives: This study investigated whether serum alpha-1-acid glycoprotein (AGP) at diagnosis could reflect the cross-sectional activity represented by the Birmingham vasculitis activity score (BVAS) and further predict poor outcomes during follow-up in patients with antineutrophil cytoplasmic antibody-associated vasculitis (AAV). Materials and Methods: This study included 70 patients with AAV. Clinical data at diagnosis, including AAV-specific indices and acute-phase reactants such as erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), were reviewed. All-cause mortality, relapse, end-stage kidney disease (ESKD), cerebrovascular accident, and acute coronary syndrome were evaluated as poor outcomes of AAV. Serum AGP was measured using the sera obtained and stored at diagnosis. Results: The median age of the patients was 63.0 years, with 29 male and 41 female patients. The median serum AGP was 150.9 μg/mL. At diagnosis, serum AGP was significantly correlated with BVAS and ESR but not CRP or serum albumin. Additionally, serum AGP showed significant correlations with the sum scores of ear–nose–throat and pulmonary manifestations; however, no significant differences in serum AGP according to each poor outcome were observed. Although serum AGP at diagnosis tended to be associated with ESKD occurrence during follow-up, serum AGP at AAV diagnosis was not significantly useful in predicting the future occurrence of poor outcomes of AAV during follow-up. Conclusions: In this study, we demonstrated the clinical utility of serum AGP at AAV diagnosis in assessing the cross-sectional activity represented by BVAS in patients with AAV for the first time.