[1] Yonsei Univ, Gangnam Severance Hosp, Internal Med, Coll Med, Seoul, South Korea
[2] Konkuk Univ, Dept Internal Med, Sch Med, Div Pulm & Allergy,Konkuk Univ Hosp, Seoul, South Korea
[3] Catholic Univ Korea, Seoul St Mary Hosp, Div Pulm & Crit Care Med, Dept Internal Med,Coll Med, Seoul, South Korea
[4] Hallym Univ, Div Pulm Allergy & Crit Care Med, Dept Internal Med, Sacred Heart Hosp, Anyang, South Korea