1. Reproductive Medicine Center, Department of Obstetrics and Gynecology, Affiliated Hospital of Guizhou Medical University, Guiyang, Guizhou 550004, P.R. China
2. Department of Gastroenterology, The Second Affiliated Hospital, Shantou University Medical College, Shantou, Guangdong 515041, P.R. China
3. Central Laboratory, Affiliated Hospital of Guizhou Medical University, Guiyang, Guizhou 550004, P.R. China
4. Department of Pathology, Affiliated Hospital of Guizhou Medical University, Guiyang, Guizhou 550004, P.R. China