1 Graduate School, Beijing University of Chinese Medicine, Beijing, China; Department of Pediatrics, China-Japan Friendship Hospital, Beijing, China.
2 Department of Pediatrics, China-Japan Friendship Hospital, Beijing, China; International Medical Services, China-Japan Friendship Hospital, Beijing, China.
3 Center for Evidence-Based Medicine, Capital Institute of Pediatrics, Beijing 100020, China. Electronic address: niuwenquan_shcn@163.com.