1. Department of Pediatrics, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul 03181, Republic of Korea
2. Biostatistics Collaboration Team, Research Core Center, National Cancer Center, Goyang 10408, Republic of Korea
3. Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul 04763, Republic of Korea