SERPINA1 and chronic obstructive pulmonary disease: Notably, serum NE in COPD have been implicated in multiple studies- altered ratio of serum NE (protease) and α-1 antitrypsin (A1AT) (antiprotease) have been shown to be directly correlated with the disease severity [7]; in vivo NE activity has been reported as a marker for cross-sectional COPD disease severity [25].