1 Department of Respiratory Medicine & Allergology, Skåne University Hospital, Lund, Sweden.
2 Bispebjerg Hospital, Copenhagen, Denmark.
3 Department of Respiratory Diseases & Allergy, Aarhus University Hospital, Arhus, Denmark.
4 Department of Respiratory Medicine & Allergology, Skåne University Hospital, Lund, Sweden ; Department of General Practice, University Medical Center Groningen and QPS-NL, Groningen, The Netherlands.