1. Department of Respiratory Medicine, Academic Medical Center, Amsterdam, the Netherlands
2. Department of Clinical Epidemiology, Biostatistics, and Bioinformatics, Academic Medical Center, Amsterdam, the Netherlands
3. Department of Respiratory Medicine, Onze-Lieve-Vrouw Hospital, Aalst, Belgium
4. Department of Respiratory Medicine, University Hospital Ghent, Ghent, Belgium
5. Department of Respiratory Medicine, Leuven University Hospitals, Leuven, Belgium
6. Papworth Clinical Trials Unit Collaboration, Papworth Hospital, Cambridge, United Kingdom