Whereas Cockayne et al. 34 showed that serum NGAL levels are positively correlated with the GOLD stage in patients with COPD (including smokers and non‐smokers), Eagan et al. 33 have reported that mean plasma NGAL levels are higher in patients with COPD but fall with increasing GOLD stage. This evidence concerns the gene LCN2 and chronic obstructive pulmonary disease.