1. Department of Medicine, Faculty of Medicine, Chulalongkorn University and King Chulalongkorn Memorial Hospital , Bangkok 10330, Thailand
2. Department of Physiology, Faculty of Medicine, Chulalongkorn University and King Chulalongkorn Memorial Hospital , Bangkok 10330, Thailand
3. Biostatistics Center, Faculty of Medicine, Chulalongkorn University , Bangkok 10330, Thailand