[1] Chung Ang Univ, Gwang Myeong Hosp, Dept Internal Med, Div Pulm Allergy & Crit Care Med, Gwangmyeong, South Korea
[2] Samsung Med Ctr, Div Pulm & Crit Care Med, Dept Med, Seoul, South Korea
[3] Seoul Natl Univ, Div Pulm & Crit Care Med, Dept Internal Med, Bundang Hosp, Seongnam, South Korea
[4] Jeju Natl Univ Hosp, Dept Internal Med, Jeju, South Korea
[5] Gyeongsang Natl Univ, Gyeongsang Natl Univ Hosp, Dept Internal Med, Coll Med, Jinju, Peoples R China
[6] Catholic Univ Korea, Div Pulm Crit Care & Sleep Med, Dept Internal Med, Eunpyeong St Marys Hosp,Coll Med, Seoul, South Korea
[7] Univ Ulsan, Ulsan Univ Hosp, Dept Internal Med, Coll Med, Ulsan, South Korea
[8] Seoul Natl Univ Hosp, Div Pulm & Crit Care Med, Dept Internal Med, Seoul, South Korea
[9] Korea Univ, Ansan Hosp, Dept Internal Med, Div Pulmonol Allergy & Crit Care Med, Ansan, South Korea
[10] Catholic Univ Korea, St Vincents Hosp, Dept Internal Med, Coll Med, Suwon, South Korea
[11] Soonchunhyang Univ, Div Allergy & Resp Dis, Cheonan Hosp, Cheonan, South Korea
[12] Univ Ulsan, Dept Pulm & Crit Care Med, Coll Med, Asan Med Ctr, Seoul, South Korea