Liu GY, et al. - In a North American population with idiopathic pulmonary fibrosis (IPF), researchers retrospectively estimated the prevalence as well as clinical importance of antineutrophil cytoplasmic antibodies (ANCAs). Two independent cohorts, ie, discovery and replication cohort, were used. The discovery cohort included patients diagnosed with IPF at the University of California San Francisco and the replication cohort comprised of patients diagnosed with IPF at the University of Chicago. All patients underwent measurements of myeloperoxidase (MPO) and proteinase 3 ANCAs. Findings revealed an uncommon prevalence of ANCA positivity in North American patients with IPF. There was no relation of ANCA positivity with baseline disease severity or transplant-free survival; however, the development of clinical vasculitis was reported in a significant proportion of patients who were MPO-positive with IPF.