MUC1 and idiopathic pulmonary fibrosis: In the multivariate analysis, only PPF was independently associated with mortality (HR 3.856; CI 1.387–10.715; P = 0.010), after adjusting other risk factors, such as age (HR 1.044; P = 0.208), male sex (HR 1.737; P = 0.326), baseline KL-6 ≥ 1000U/mL (HR 2.453; P = 0.164), baseline albumin (HR 0.549; P = 0.054), radiologic UIP pattern (HR 2.075; P = 0.110), and baseline DLco (HR 0.979; P = 0.210).