The aim of this study is to serially analyze KL-6 in idiopathic pulmonary fibrosis (IPF) patients after 24 months of Nintedanib and to investigate its biomarker potential in patients with IPF and lung cancer with respect to fibrotic hypersensitivity pneumonitis patients, pulmonary fibrosis associated with autoimmune diseases group and healthy controls. Here, MUC1 is linked to hypersensitivity pneumonitis.