CRP and anti-neutrophil cytoplasmic antibody-associated vasculitis: Receiver operating characteristic (ROC) curve analysis was carried out for serum IL-18, C-reactive protein (CRP), and erythrocyte sedimentation rate (ESR) levels in patients with AAV to investigate the clinical significance of serum IL-18 levels in pathogenesis of AAV and the effect of NLR changes on the prognosis.