1. Department of Nephrology, the Affiliated Hospital of Qingdao University, Qingdao, Shandong, China.
2. Department of Nephrology, the People's Hospital of Chengyang, Qingdao, Shandong, China.
3. Department of Nephrology, the Affiliated Hospital of Qingdao University, Qingdao, Shandong, China. liuxuemei@qdu.edu.cn