1. Division of Pulmonary, Allergy and Critical Care Medicine, Department of Internal Medicine, Hallym University Kangdong Sacred Heart Hospital, Hallym University College of Medicine, Seoul, Korea.
2. Lung Research Institute, Hallym University College of Medicine, Chuncheon, Korea.
3. Division of Pulmonary, Allergy and Critical Care Medicine, Department of Internal Medicine, Inje University Busan Paik Hospital, Inje University College of Medicine, Busan, Korea.
4. Department of Laboratory Medicine, Inje University Busan Paik Hospital, Inje University College of Medicine, Busan, Korea.
5. Division of Respiratory and Critical Care Medicine, Department of Internal Medicine, Korea University Guro Hospital, Seoul, Korea.
6. Department of Internal Medicine, Jeju National University Hospital, Jeju, Korea.