[1] Yonsei Univ, Severance Hosp, Inst Chest Dis, Dept Internal Med,Coll Med,Div Pulmonol, 50-1 Yonsei Ro, Seoul 03722, South Korea
[2] Hanyang Univ, Guri Hosp, Div Pulm & Crit Care Med, Coll Med, Guri, South Korea
[3] Inha Univ, Inha Univ Hosp, Dept Internal Med, Div Pulm & Crit Care Med,Coll Med, Incheon, South Korea
[4] Ewha Womans Univ, Dept Internal Med, Div Pulm & Crit Care Med, Coll Med, Seoul, South Korea
[5] Hallym Univ, Coll Med, Dept Internal Med, Kangdong Sacred Heart Hosp,Lung Res Inst, Seoul, South Korea
[6] Seoul Natl Univ, Bundang Hosp, Dept Internal Med, Div Pulm & Crit Care Med,Coll Med, Seongnam, South Korea
[7] Kyung Hee Univ Hosp Gangdong, Div Pulm & Crit Care Med, Seoul, South Korea
[8] Univ Ulsan, Asan Med Ctr, Dept Pulm & Crit Care Med, Coll Med, Seoul, South Korea
[9] Sungkyunkwan Univ, Samsung Med Ctr, Div Pulm & Crit Care Med, Sch Med, Seoul, South Korea
[10] Keimyung Univ, Dept Internal Med, Sch Med, Daegu, South Korea
[11] Soonchunhyang Univ, Dept Internal Med, Seoul Hosp, Seoul, South Korea
[12] Seoul Natl Univ Hosp, Dept Internal Med, Div Pulm & Crit Care Med, Seoul, South Korea