1. Respiratory Department, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain
2. Biomedical Research Institute Sant Pau, Barcelona, Spain
3. Hospital Comarcal de Mollet, Mollet del Vallés, Spain
4. Scottish Centre for Respiratory Medicine, University of Dundee, Dundee, United Kingdom
5. Department of Respiratory Medicine, AZ Nikolaas, Sint-Niklaas, Belgium; and
6. Department of Respiratory Medicine, UZ Leuven, Leuven, Belgium