Sputum colour as a simplified effective biomarker for clinical assessment of bronchiectasis

Bronchiectasis is a structural lung disease characterised by chronic airway inflammation due to various aetiologies, with a vicious circle of recurrent infections, chronic inflammation, impaired mucociliary clearance and structural damage that collectively result in clinical progression [1]. The most prominent clinical manifestations of bronchiectasis are chronic cough and mucopurulent sputum production, the consequence of airway mucus hypersecretion and heightened inflammatory responses which could predispose to irreversible airway destruction [2, 3]. Amid this vicious circle of bronchiectasis pathogenesis is chronic inflammation characterised by predominantly neutrophilic inflammation. In light of a paucity of validated direct laboratory testing methods for assessing neutrophilic inflammation in routine clinical practice, researchers have developed a novel lateral flow device to evaluate the neutrophil elastase activity from sputum in bronchiectasis (NEATstik), whose grading correlated significantly with the risks of airway infection and future exacerbations [4]. Nevertheless, enormous challenges remain, especially in the resource-constrained areas where supply of such tools falls short. The exploration of a simpler, patient-friendly bedside assessment tool would therefore open up new avenues for the management of bronchiectasis, particularly in the community setting and in many developing countries. Sputum colour is a simple and effective biomarker for assessing severity and prognosis of bronchiectasis