Receiver-operating characteristic curve analysis of anti-neutrophil cytoplasmic antibodies (ANCA) against proteinase 3 (PR3) and myeloperoxidase (MPO) levels by classical and automated multiplex microbead assay testing.

PR3- and MPO-ANCA were determined by enzyme-linked immunosorbent assay (ELISA) and multiplex CytoBead microbead assay (MIA) in 118 patients with ANCA-associated vasculitis as disease criterion and in 300 patients with autoimmune and gastrointestinal diseases, 49 with infectious disorders, and 125 blood donors (BD) as control criterion. MPO-ANCA detected by MIA demonstrated a significantly higher AUC compared with those determined by ELISA. AUC, area under the curve; CI, confidence interval.