Non-invasive assessment of small airway remodelling in smokers.

Smoking associated COPD progression is likely to be directly linked to differential injury and repair dynamics in small airways (SA). Although IL8 is a well-accepted marker for injured airway epithelium, Clara cells [the predominant proliferating cells in SA] and SCGB1A1 protein [their major secretory product] have only recently emerged as potential SA repair markers. We therefore postulate that the SCGB1A1/IL8 ratio in the airways of smokers would be inversely associated with physiological, radiological and clinical measures of COPD.