Chronic obstructive pulmonary disease (COPD) is characterized by high levels of protease activity leading to degradation of elastin followed by loss of elasticity of the lung and the development of emphysema. Elastin is an essential structural component of the lung parenchyma to support the expansion and recoil of the alveoli during breathing. The lung extracellular matrix is vulnerable to pathological structural changes upon upregulation of serine proteases, including cathepsin G (CG) and proteinase 3 (PR3). In this study, we explored the diagnostic features of elastin neo-epitopes generated by CG and PR3. Two novel competitive enzyme-linked immunosorbent assays (ELISA) measuring CG and PR3 generated elastin fragments (EL-CG and ELP-3 respectively) were developed for assessment in serum. Both assays were technically robust and biologically validated in serum from patients with COPD. Serological levels of both elastin fragments were significantly elevated in patients with COPD compared to healthy controls. These data suggest that EL-CG and ELP-3 may serve as plausible biologic markers of destructive changes in COPD. (C) 2018 Elsevier Inc. All rights reserved.