1. Division of Pulmonary, Allergy, and Critical Care Medicine, Department of Internal Medicine, Hallym University Kangnam Sacred Heart Hospital, Seoul, Korea
2. Lung Research Institute, Hallym University College of Medicine, Chuncheon, Korea
3. Department of Internal Medicine, Hanyang University College of Medicine, Seoul, Korea
4. Biostatistical Consulting and Research Lab, Medical Research Collaborating Center, Hanyang University, Seoul, Korea
5. Department of Internal Medicine, Hanyang University College of Medicine, 222 Wangsimni-ro, Seongdong-gu, Seoul 04763, Korea