[1] Brigham & Womens Hosp, Channing Lab, Boston, MA 02115 USA
[2] Tufts Med Ctr, Inst Clin Res & Hlth Policy Studies, Boston, MA USA
[3] Haukeland Hosp, N-5021 Bergen, Norway
[4] Univ Cambridge, Dept Med, Cambridge Inst Med Res, Cambridge CB2 2QQ, England
[5] GlaxoSmithKline, Res Triangle Pk, NC USA
[6] Johns Hopkins Sch Publ Hlth, Baltimore, MD USA
[7] Univ Colorado Denver, Colorado Sch Publ Hlth, Aurora, CO USA
[8] Natl Jewish Med & Res Ctr, Denver, CO USA
[9] Harvard Univ, Harvard Sch Publ Hlth, Boston, MA 02115 USA
[10] Brigham & Womens Hosp, Div Pulm & Crit Care Med, Boston, MA 02115 USA
[11] Harvard Univ, Sch Med, Boston, MA USA