Anti-neutrophil cytoplasmic antibodies in interstitial lung disease: results from a cross-sectional study and meta-analysis.

This study aims to investigate the prevalence, clinical characteristics, and prognostic significance of anti-neutrophil cytoplasmic antibodies (ANCA) across different subtypes of interstitial lung disease (ILD), specifically idiopathic pulmonary fibrosis (IPF), connective tissue disease-associated ILD (CTD-ILD) without ANCA-associated vasculitis (AAV), and AAV-ILD. A cross-sectional study was conducted to evaluate the positivity rate and clinical characteristics of ANCA in ILD. In the following meta-analysis, PubMed, Web of Science and Scopus were searched for eligible studies reporting positivity rate of ANCA in ILD. The pooled positivity rates of ANCA, MPO and PR3 in ILD were calculated, and survival outcome between ANCA-positive and ANCA-negative ILD patients were compared. Sensitivity analyses, subgroup analyses and meta-regression was also conducted. A total of 217 ILD patients were enrolled in this cross-sectional study, with an ANCA positivity rate of 7%. In the meta-analysis, with 24 studies and 4,424 patients, the pooled positivity rate of ANCA in IPF, CTD-ILD without AAV, and AAV-ILD were 9%, 15% and 97%, respectively. In patients with IPF, patients with ANCA positivity were more likely to develop honeycombing (OR 2.70, 95%CI 1.09, 6.70, p = 0.03). No significant difference was observed in survival time between IPF patients with or without ANCA positivity (HR 1.18, 95%CI 0.73, 1.90). The positivity rate of ANCA varies significantly across different subtypes of ILD. Future research should focus on the characteristics and prognostic value of ANCA positivity in other ILD subtypes.