Liu GY, et al. - In this retrospective study with two independent cohorts, researchers examined a North American population with idiopathic pulmonary fibrosis (IPF) to estimate the prevalence of antineutrophil cytoplasmic antibodies (ANCA) antibodies as well as to assess their clinical significance. Patients diagnosed with IPF at the University of California San Francisco (discovery cohort) and the University of Chicago (replication cohort) were included. ANCA-positive patients vs ANCA-negative patients were more likely to be female and more likely to exhibit some ground glass opacities on computed tomography. In North American patients with IPF, an uncommon prevalence of ANCA-antibody positivity was reported. In the discovery and replication cohorts, ANCA-antibody positivity at the time of diagnosis was present in 14/353 and 20/392 of patients with IPF, respectively. There was no link of ANCA-antibody positivity with baseline disease severity or transplant-free survival; however, the development of clinical vasculitis was seen in a significant proportion of myeloperoxidase-positive IPF patients.