MPO and idiopathic pulmonary fibrosis: At the time of IPF diagnosis or during follow-up, up to 20% of patients present with ANCA positivity, without clinical manifestations of systemic vasculitis.[9–12] The most frequently detected ANCAs are anti-MPO and much less often antiproteinase antibodies , antielastase, antilactoferrin, or nonspecific ANCA positivity.