[1] McGill Univ, Hlth Ctr, Res Inst, Resp Epidemiol & Clin Res Unit, Montreal, PQ, Canada
[2] McGill Univ, Dept Med, Resp Div, Hlth Ctr, Montreal, PQ, Canada
[3] Univ Texas MD Anderson Canc Ctr, Dept Pulm Med, Houston, TX 77030 USA
[4] Virginia Commonwealth Univ, Div Pulm & Crit Care Med, Dept Internal Med, Richmond, VA USA