Patterns of Interstitial Lung Disease and Prognosis in Antineutrophil Cytoplasmic Antibody-Associated Vasculitis

Interstitial lung disease (ILD) is a common pulmonary manifestation of antineutrophil cytoplasmic antibody-associated vasculitis (AAV).We aimed to clarify the clinical predictors of mortality in a cohort of patients with AAV-related ILD (AAV-ILD).We retrospectively identified AAV-ILD patients seen at Peking University First Hospital from January 2010 to June 2020 and manually screened for study inclusion. Baseline computed tomography (CT) images were further classified as nonspecific interstitial pneumonia (NSIP), usual interstitial pneumonia (UIP), organizing pneumonia (OP), and unclassified ILD. Disease characteristics and other pulmonary findings including pulmonary function test and bronchoalveolar lavage (BAL) were also evaluated. Multivariable Cox regression analysis was performed to identify clinical predictors of mortality.The cohort included 204 patients with AAV-ILD, 152 had UIP on CT (AAV-UIP), 39 had NSIP on CT (AAV-NSIP), 3 had OP, and 10 had unclassified ILD. Microscopic polyangiitis was more prevalent in patients with UIP, while granulomatosis with polyangiitis was more common in the NSIP and OP groups, and eosinophilic granulomatosis with polyangiitis was more frequent in patients with unclassified ILD. ILD diagnosis before AAV was more common in patients with either UIP or NSIP patterns. During the median follow-up of 40 months, 44 (21.6%) patients died. One- and 5-year overall survival rates were 88.2% (95% CI, 83.7-92.7%) and 81.0% (95% CI, 74.9-87.1%) for the entire cohort. Patients with UIP patterns had the worst prognosis, while those with NSIP patterns had the best long-term outcome. Specifically, patients with UIP patterns had an approximately 5-fold risk of death compared to those with NSIP. After controlling for potential confounding factors, we observed that each 10% increase in the BAL fluid neutrophil percentage was associated with nearly a 20% increased risk of death (HR 1.195, 95% CI 1.018-1.404).Clinical characteristics and survival differ between subgroups defined by CT patterns. BAL fluid neutrophilia is an independent predictor of mortality among AAV-ILD patients, and therefore, the clinical utility of BAL at the time of AAV diagnosis should be considered.