1. Blood Purification Center, Nanhai Hospital of Southern Medical University, Foshan, Guangdong 528244, P.R. China
2. Department of Nephrology, The People's Hospital of Guangxi Zhuang Autonomous Region, Nanning, Guangxi 530021, P.R. China
3. Department of Nephrology, Zhujiang Hospital of Southern Medical University, Guangzhou, Guangdong 510282, P.R. China