A point-of-care neutrophil elastase activity assay identifies bronchiectasis severity, airway infection and risk of exacerbation

Introduction: Neutrophil elastase activity in sputum can identify patients at high risk of airway infection and exacerbations in bronchiectasis. Application of this biomarker in clinical practice is limited, because no point-of-care test is available. We tested whether a novel semi-quantitative lateral flow device (neutrophil elastase airway test stick - NEATstik (R)) can stratify bronchiectasis patients according to severity, airway infection and exacerbation risk. Methods: Sputum samples from 124 patients with stable bronchiectasis enrolled in the UK and Spain were tested using the NEATstik (R), which scores neutrophil elastase concentration from 0 (6. Severity of disease, airway infection from sputum culture and exacerbations over the 12 months were recorded. An independent validation was conducted in 50 patients from Milan, Italy. Measurements and main results: Patients had a median age of 69 years and forced expiratory volume in 1 s (FEV1) 69%. High neutrophil elastase activity was associated with worse bronchiectasis severity using the bronchiectasis severity index (p=0.0007) and FEV1 (p=0.02). A high NEATstik (R) grade was associated with a significant increase in exacerbation frequency, incident rate ratio 2.75 (95% CI 1.63-4.64, p6 was 103 days compared to 278 days. The hazard ratio was 2.59 (95% CI 1.71-3.94, p