1. Department of Laboratorial Science and Technology, School of Public Health, Peking University, Beijing 100191, P.R. China
2. Department of Pathology, the Affiliated Hospital of Qingdao University, Qingdao, Shandong 266003, P.R. China
3. Department of Epidemiology and Biostatistics, School of Public Health, Peking University, Beijing 100191, P.R. China