DUOX1 and chronic obstructive pulmonary disease: Correlation of epithelial DUOX1 staining scores with parameters of lung function indicated a striking positive association of DUOX1 score with spirometric parameters (FEV1, FVC) and diffusing capacity (Dlco, diffusing capacity for carbon monoxide, which indicates loss of alveolar surface area and capillary bed, impairing diffusion; ref. 30), both of which were based on inclusion of all subjects (including controls, Figure 1C and Table 1) and patients with COPD (GOLD II vs. GOLD IV) alone (Table 1).