1. Department of Epidemiology, College of Preventive Medicine, Army Military Medical University, Chongqing 400038, P.R. China
2. Department of Hepatobiliary Surgery, The First Affiliated Hospital of Army Military Medical University, Chongqing 400038, P.R. China
3. Department of Pediatrics, Banan People's Hospital of Chongqing, Chongqing 401320, P.R. China
4. Department of Anesthesia, The First Affiliated Hospital of Army Military Medical University, Chongqing 400038, P.R. China
5. The Second Clinical College, Chongqing Medical University, Chongqing 400010, P.R. China
6. College of Preventive Medicine, Southwest Medical University, Luzhou, Sichuan 646000, P.R. China