LCN2 and chronic obstructive pulmonary disease: Similarly, the level of proMMP‐9/NGAL was markedly higher in the COPD‐S group (17.9 ng/ml) than in the healthy‐S group (10.42 ng/ml; P = 0.01 versus COPD‐S) and the COPD‐NS group (7.87 ng/ml; P = 0.02 versus COPD‐S; Fig. 1B).