1. M.D. Program, Peking Union Medical College, Chinese Academy of Medical Science , No. 9 Dongdansantiao, Dongcheng District , 100730 Beijing, China
2. Department of Internal Medicine, Peking Union Medical College Hospital, Chinese Academy of Medical Science , No. 1, Shuaifuyuan, Wangfujing Street, Dongcheng District , 100730 Beijing, China
3. Department of General Internal Medicine, Peking Union Medical College Hospital, Chinese Academy of Medical Science , No. 1, Shuaifuyuan, Wangfujing Street, Dongcheng District , 100730 Beijing, China