Assessment of airway neutrophils by sputum colour: correlation with airways inflammation

Background-Airway inflammation, with recruitment of neutrophils to the airw ay lumen, results in purulent secretions and a variety of potential adverse consequences for patients with chronic bronchitis and bronchiectasis. We h ypothesised that gradations of sputum colour would correlate directly with the myeloperoxidase content of sputum and with various other indicators of the activity and consequences of bronchial diseases. Methods-To test this hypothesis, we quantified sputum colour by reference t o a sensitive nine point colour chart and correlated this assessment with i ndices of a number of inflammatory mediators in sputum. Results-The results indicate that standardised visual measurements of sputu m colour correlated strongly with myeloperoxidase, interleukin 8, leucocyte elastase (both activity and total quantity), sputum volume, protein leak, and secretory leucocyte proteinase inhibitor (p <0.001 for all). In additio n, there was a strong direct correlation between leucocyte elastase and bot h myeloperoxidase (p <0.003) and sputum volume (p <0.001), but a strong neg ative correlation with secretory leucocyte proteinase inhibitor (p <0.001). Conclusions-These results indicate that sputum colour graded visually relat es to the activity of the underlying markers of bronchial inflammation. The results of this simple visual analysis of sputum provides guidance concern ing underlying inflammation and its damaging potential. It also provides a useful scientific tool for improving the monitoring of chronic airways dise ases and response to treatment.