MUC1 and idiopathic pulmonary fibrosis: No significant differences in baseline KL-6 concentrations were observed between IPF (1194 (IQR: 841–1864) U/mL) and fNSIP (1458 (IQR: 883–1905) U/mL), but the median KL-6 levels were significantly higher in ILD patients compared to healthy controls (p < 0.0001).