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