[1] Royal Victoria Hosp, Montreal Chest Inst, Resp Epidemiol & Clin Res Unit, Montreal, PQ H2X 2P4, Canada
[2] McGill Univ, Ctr Hlth, St Marys Hosp, Dept Med, Montreal, PQ, Canada
[3] Univ Calgary, Dept Med, Calgary, AB, Canada
[4] Family Med, Halifax, NS, Canada
[5] AstraZeneca Canada Inc, Mississauga, ON, Canada