MUC1 and chronic obstructive pulmonary disease: In addition, some of the patients have more than one pulmonary disease; as ILD is likely to be combined with lung cancer, COPD, and TB, patients with these diseases would have abnormal levels of KL-6, and most of them were excluded in clinical trials (15, 18, 20), the clinical use of KL-6 levels among these overlap patients should be comprehensively assessed.