Figure 2: Individual mucin concentrations and COPD severity, and the association between lung function and mucin subtypes and their ratio.

(A–C) Absolute mean concentrations of MUC5B and MUC5AC, and their ratio, in never-smoker controls, ever-smokers without evidence of COPD by spirometry (at-risk; formerly known as GOLD stage 0), and ever-smokers with mild (GOLD1), moderate (GOLD2), and severe (GOLD3) COPD. (D–F) Mean FEV1 percentage predicted in tercile groups of MUC5AC concentration, MUC5B concentration, and MUC5AC/MUC5B ratio. (G–I) Mean FEV1/FVC in tercile groups of MUC5AC concentration, MUC5B concentration, and MUC5AC/MUC5B ratio. Error bars represent SEM. Sample size for each group is shown in the middle of the bar. COPD=chronic obstructive pulmonary disease. FVC=forced vital capacity. GOLD=Global Initiative for Chronic Obstructive Lung Disease. *p≤0.01. †p≤0.005. ‡p≤0.001. §p≤0.05.