According to results of a study conducted at the University of Oxford in the United Kingdom, levels of neutrophil elastase (NE) in patients with chronic obstructive pulmonary disease (COPD) are related closely to neutrophil inflammation, and thus have the potential to be a viable biomarker that is indicative of a bacterial-associated exacerbation. The findings were published in Respiratory Research.
Recognizing that COPD is associated predominantly with neutrophil inflammation and that active NE is a serine proteinase secreted by neutrophils as a response to inflammation and pathogen invasion, investigators aimed to explore whether NE could be used as a biomarker for bacterial infection in patients with COPD. NE was quantified with the use of the ProteaseTag Active NE Immunoassay kit (ProAxis; Belfast, Northern Ireland) from the sputum of patients with COPD at stable state, during disease exacerbation, and at a 2-week posttreatment visit.
The researchers measured NE in 90 samples obtained from 30 participants with COPD, 18 of whom were men. The mean participant age was 65 years (range, 45-81 years); the mean forced expiratory volume in 1 second was 47%±18%. At stable state, the geometric mean of NE was 2454 ng/mL (95% CI, 1460-4125 ng/mL). At a COPD exacerbation, a significant increase in NE levels was observed (P =.003). NE levels were higher when there was a bacterial-associated disease exacerbation (log difference, 3.873 ng/mL; 95% CI, 1.396-10.740 ng/mL; P =.011).
NE was shown to be a reliable predictor of a bacterial-associated disease exacerbation (area under the received operator characteristic curve, 0.812; 95% CI, 0.657-0.968), with a cutoff of 3034 ng/mL having both a specificity and a sensitivity of 77%.
The investigators concluded that the results of this study might be used to guide antibiotic therapy at the onset of a COPD exacerbation, and thus warrant additional exploration.
Thulborn SJ, Mistry V, Brightling CE, Moffitt KL, Ribeiro D, Bafadhel M. Neutrophil elastase as a biomarker for bacterial infection in COPD [published online July 30, 2019]. Respir Res. 2019;20(1):170.