Induced sputum and bronchial hyperresponsiveness in COPD patients

Introduction : Bronchial hyperresponsiveness (BHR) is often thought to be a hallmark of asthma, yet it has been shown to occur in up to two-thirds of patients with COPD as well. Whereas in asthma, BHR is associated with both baseline level of FEV 1 and eosinophilic airway inflammation, the factors underlying BHR in COPD are not completely known. Objectives : We evaluated the relationship between BHR, lung function and airway inflammation in COPD patients. Methods : Twenty-six patients with stable mild-to-moderate COPD (age 67±8 yrs, 5 F; FEV 1 67±18%, FEV 1 /VC 53±11%) were studied. All patients were stable and steroids free. We investigated lung function, including body plethysmography, reversibility, diffuse lung capacity ( T L,CO/VA%), provocative dose of methacholine causing a 20% fall in FEV 1 , and sputum induction. Patients were considered to be hyperresponsive when they had a PD 20 ≤1600 µg. Results : Twenty-one patients completed the procedures. Seven out of 21 patients (33%) were hyperresponsive (PD 20 mean 378 µg, range 95-872 µg). No differences were observed in lung function and in the induced sputum total and differential cell counts, between hyperresponsive and non-hyperresponsive patients. Five patients had sputum eosinophils > 3%, but no differences were observed in lung function and BHR between patients with and without sputum eosinophils. Conclusions : Our preliminary study confirms that BHR can occur in a considerable number of COPD patients. In contrast with previous data, we did not found differences between hyperresponsive and non-hyperresponsive patients in terms of airway inflammation. Further data are needed to elucidate the relationships between BHR, lung function, and airway inflammation in COPD.