[1] Aarhus Univ Hosp, Dept Resp Dis & Allergy, Noerrebrogade 44, DK-8000 Aarhus, Denmark
[2] Univ Tartu, Dept Resp Dis, Tallinn, Estonia
[3] Oslo Univ Hosp, Dept Resp Dis, Oslo, Norway
[4] Univ Helsinki, Dept Resp Dis, Helsinki, Finland
[5] Univ Helsinki, Heart & Lung Ctr, Helsinki, Finland
[6] Helsingin Univ, Cent Hosp, Helsinki, Finland
[7] Natl Univ Hosp Iceland, Landspitali, Dept Resp Med & Sleep, Reykjavik, Iceland
[8] Univ Iceland, Sch Hlth Sci, Fac Med, Reykjavik, Iceland
[9] Karolinska Univ Hosp, Lung Allergy Clin, Karolinska Inst, Dept Med Solna, Stockholm, Sweden