[1] Univ Roma Tor Vergata, Unit Resp Dis, Dept Internal Med, I-00133 Rome, Italy
[2] Univ Roma La Sapienza, Rome, Italy
[3] Univ Genoa, Genoa, Italy
[4] Univ Florence, I-50121 Florence, Italy
[5] Colt Res Labs, Sch Med, Edinburgh, Midlothian, Scotland
[6] Kings Coll London, London, England
[7] Univ London Imperial Coll Sci Technol & Med, Natl Heart & Lung Inst, London SW7 2AZ, England
[8] Univ London, St Georges Hosp, London WC1E 7HU, England
[9] Kings Coll Hosp London, Sch Med, Sackler Inst Pulm Pharmacol, London, England
[10] UCL, London WC1E 6BT, England
[11] Birmingham Heartlands Hosp, Birmingham, W Midlands, England
[12] Queen Elizabeth Hosp, Birmingham, W Midlands, England
[13] Univ Hosp Covertry, Coventry, W Midlands, England
[14] Univ Hosp Warcickshire, Coventry, W Midlands, England
[15] Aintree Univ Hosp NHS Fdn Trust, Liverpool, Merseyside, England
[16] Univ Michigan, Sch Med, Ann Arbor, MI 48109 USA
[17] Caritas St Elizabeth Med Ctr, Boston, MA USA
[18] Dartmouth Hitchcock Med Ctr, Lebanon, NH 03766 USA
[19] Natl Jewish Med & Res Ctr, Denver, CO USA
[20] Univ Washington, Seattle, WA 98195 USA
[21] Leiden Univ, Med Ctr, Leiden, Netherlands
[22] Erasmus MC Univ, Med Ctr Rotterdam, Rotterdam, Netherlands
[23] Univ Hosp Maastricht, Maastricht, Netherlands
[24] Hosp Clin Barcelona, Barcelona, Spain