MUC1 and chronic obstructive pulmonary disease: Mean induced sputum level of KL-6 was higher in the middle aged/elderly males with COPD when compared to the non-smokers in the group (middle aged/elderly male non-smokers 54 ± 13 U/ml, middle aged/elderly males with COPD 232 ± 64 U/ml; p = 0.021) (Figure 2B).