Clinical Implication of Proteinase-3-antineutrophil Cytoplasmic Antibody in Patients with Idiopathic Interstitial Pneumonias.

Abstract

The clinical significance of proteinase-3-antineutrophil cytoplasmic antibody (PR3-ANCA) positivity is not well established in idiopathic interstitial pneumonia (IIP) patients. We aimed to determine the clinical features of PR3-ANCA-positive IIP patients. We retrospectively reviewed 377 consecutive IIP patients; of these, 360 patients had PR3-ANCA and myeloperoxidase-antineutrophil cytoplasmic antibody test results available. The clinical features of PR3-ANCA-positive IIP patients and control ANCA-negative idiopathic pulmonary fibrosis patients (ANCA-negative IPF) were compared. Sixteen patients (4.4%) were PR3-ANCA-positive IIP and 94 (26%) were ANCA-negative IPF. The median age at diagnosis (72 vs. 70years, P=0.17) and proportion of males (75 vs. 89%, P=0.12) in PR3-ANCA-positive IIP and ANCA-negative IPF patients, respectively, were not significantly different. Radiologically, the HRCT patterns of PR3-ANCA-positive IIP patients varied (UIP, n=3, 18.8%; possible UIP, n=3, 18.8%; NSIP, n=5, 31.3%; unclassifiable CT pattern, n=5, 31.3%) more than those of ANCA-negative IPF patients (UIP, n=69, 73.4%; possible UIP, n=25, 26.6%; P<0.001). No PR3-ANCA-positive IIP patients developed ANCA-associated vasculitis. The 5-year survival rate was 50% in PR3-ANCA-positive IIP patients and 52% in ANCA-negative IPF patients with no significant difference (P=0.96 by log-rank test). The HRCT patterns of PR3-ANCA-positive IIP patients varied more than those of the IPF patients, but the clinical features of high IIP-onset age and male predominance were similar between the groups. Furthermore, PR3-ANCA-positive IIP patients had a poor prognosis similar to that of IPF patients.