Clinical implications of peripheral eosinophil count at diagnosis in patients newly diagnosed with microscopic polyangiitis and granulomatosis with polyangiitis

Abstract

Background: This study investigated the clinical implications of peripheral eosinophil count at diagnosis in estimating cross-sectional antineutrophil cytoplasmic antibody-associated vasculitis (AAV) activity and predicting all-cause mortality during follow-up in patients newly diagnosed with microscopic polyangiitis (MPA) and granulomatosis with polyangiitis (GPA). Methods: This study included 224 immunosuppressive drug-naïve patients with peripheral eosinophil count at diagnosis < 1,000/mm3. The Birmingham Vasculitis Activity Score (BVAS), the Five-Factor Score (FFS), erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) at diagnosis were assessed. Results: The median age of the 224 patients (152 MPA and 72 GPA) was 62.0 years; 35.3% of them were men. At diagnosis, peripheral eosinophil count was significantly correlated with BVAS (P = 0.001), FFS (P = 0.046), ESR (P < 0.001), and CRP (P < 0.001). Deceased patients had a significantly higher median peripheral eosinophil count at diagnosis than surviving patients (310.0/mm3 vs. 170.0/mm3, P = 0.004). In addition, patients with MPA and those with cardiovascular and renal manifestations at diagnosis exhibited significantly higher peripheral eosinophil counts than those without. When the optimal cut-off of peripheral eosinophil count at diagnosis for all-cause mortality during follow-up was set at 175.0/mm3, Patients with peripheral eosinophil count at diagnosis ≥ 175.0/mm3 exhibited a significantly lower cumulative patients’ survival rate than those with peripheral eosinophil count at diagnosis < 175.0/mm3 (P = 0.008). Conclusions: This study was the first to demonstrate that peripheral eosinophil count at diagnosis could estimate cross-sectional AAV activity at diagnosis and contribute to predicting all-cause mortality during follow-up in MPA and GPA patients.