1. Section for Clinical Epidemiology and Biostatistics; Faculty of Medicine; Ramathibodi Hospital; Mahidol University; Bangkok; Thailand
2. Centre for Clinical Epidemiology and Biostatistics; School of Medicine and Public Health; University of Newcastle; Hunter Medical Research Institute; Newcastle; New South Wales; Australia
3. Department of Family Medicine; Faculty of Medicine; Ramathibodi Hospital; Mahidol University; Bangkok; Thailand
4. Department of Orthopaedics; Faculty of Medicine; Ramathibodi Hospital; Mahidol University; Bangkok; Thailand