Neutrophil elastase (NE) is a 29kDa serine protease released from the azurophilic granules of neutrophils. It may be directly involved in the pathogenesis and disease progression in cystic fibrosis, bronchiectasis and COPD through the degradation of airway elastin and by impairing host defence. Areas covered: Measurement of NE activity has emerged as a promising biomarker strategy in inflammatory lung disease. The authors review studies where NE activity has been linked with clinical outcomes such as lung function decline, exacerbation frequency or other cross-sectional and longitudinal markers of disease severity. In this article the evidence for NE measurement, and the strengths and weaknesses of a commercially available immunoassay which can specifically detect NE activity in human biological samples such as sputum and bronchoalveolar lavage are reviewed. Expert commentary: NE is a promising biomarker for stratifying severity disease. NE also appears to be responsive to antibiotic and other treatments, potentially therefore allowing it to be used as an indicator of treatment response in clinical trials.
Keywords: Bronchiectasis; COPD; cystic fibrosis; elastase; neutrophils.