Significantly decreased SCGB1A1 levels (ng/mL; interquartile range) were detected in BMS-COPD (1.61; 1.29–2.44) and TS-COPD (1.80; 1.38–2.51) subjects compared to both TS-CONTROL (3.27; 2.90–3.51) and healthy controls (5.07; 4.47–7.20) (Figure 2a). Here, SCGB1A1 is linked to chronic obstructive pulmonary disease.