1. Ministry of Public Health; Institute of Medical Research and Technology Assessment, Dept of Medical Services; Tiwanon Nonthaburi Thailand 11000
2. Chiangmai University; Department of Surgery; Suthep Chiangmai Thailand 50200
3. Lerdsin Hospital; Department of Surgery; Srilom Bangrak Bangkok Thailand 10500
4. Khon Kaen University; Department of Biostatistics and Demography, Faculty of Public Health; 123 Mitraparb Road Amphur Muang Khon Kaen Thailand 40002