Relationship between airway inflammation and the frequency of exacerbations in patients with smoking related COPD

Background-Patients with more frequent exacerbations of chronic obstructive pulmonary disease (COPD) may have increased bronchial inflammation. Airway inflammation was measured in patients who had been thoroughly investigated with full pulmonary function testing, thoracic HRCT scanning, and sputum m icrobiology to examine further the relationship between exacerbation freque ncy and bronchial inflammation. Methods-Airway inflammation (spontaneous sputum sol phase myeloperoxidase ( MPO), elastase, leukotriene (LT)B-4, interleukin (IL)-8, secretory leukopro tenase inhibitor (SLPI), protein leakage) and serum levels of C reactive pr otein (CRP) were compared in 40 patients with stable, smoking related COPD, divided into those with frequent (greater than or equal to3/year) or infre quent (less than or equal to2/ year) exacerbations according to the number of primary care consultations during the preceding year. The comparisons we re repeated after excluding eight otherwise clinically indistinguishable pa tients who had tubular bronchiectasis on the HRCT scan. Results-Patients with frequent (n=12) and infrequent (n=28) exacerbations w ere indistinguishable in terms of their clinical, pulmonary function, and s putum characteristics, CRP concentrations, and all of their bronchial infla mmatory parameters (p>0.05). The patients without evidence of tubular bronc hiectasis (n=32) were equally well matched but the sputum concentrations of SLPI were significantly lower in the frequent exacerbators (n=8) in this s ubset analysis (p<0.05). Conclusions-There are several clinical features that directly influence bro nchial inflammation in COPD. When these were carefully controlled for, pati ents with more frequent reported exacerbations had lower sputum concentrati ons of SLPI. This important antiproteinase is also known to possess antibac terial and antiviral activity. Further studies are required into the nature of recurrent exacerbations and, in particular, the regulation and role of SLPI in affected individuals.