1. Department of Internal Medicine, Beijing Obstetrics and Gynecology Hospital, Capital Medical University, Beijing 100026, P.R. China
2. Department of Emergency, Beijing Chaoyang Hospital (Jingxi Campus), Capital Medical University, Beijing 100043, P.R. China
3. Department of Infectious Diseases, Beijing Friendship Hospital, Capital Medical University, Beijing 100050, P.R. China
4. Central Laboratory, Beijing Obstetrics and Gynecology Hospital, Capital Medical University, Beijing 100026, P.R. China