1. Department of Pediatrics, Soonchunhyang University Bucheon Hospital, Soonchunhyang University School of Medicine, Bucheon, South Korea;
2. Department of Pediatrics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea;
3. Research Institute for Future Medicine, Samsung Medical Center, Seoul, South Korea;
4. Statistics and Data Center, Samsung Medical Center, Seoul, South Korea;
5. Department of Pediatrics, Inje University Busan Paik Hospital, Inje University College of Medicine, Busan, South Korea