Renal Division, Department of Medicine, Peking University First Hospital, Beijing, China. Institute of Nephrology, Peking University, Beijing, China. Key Laboratory of Renal Disease, Ministry of Health of China, Beijing, China. Key Laboratory of Chronic Kidney Disease Prevention and Treatment, Ministry of Education, Beijing, China. Department of Nephrology, Capital Medical University Fuxing Hospital, Beijing, China. Department of Nephrology, The Fourth Hospital of Hebei Medical University, Shijiazhuang, Hebei, China. Nephrotic Blood Purification Center, Tianjin Third Central Hospital, Tianjin, China. Department of Nephrology, Beijing Miyun County Hospital, Beijing, China. Department of Nephrology, General Hospital of Tianjin Medical University, Tianjin, China. Department of Nephrology, Beijing Shijitan Hospital, Beijing, China. Department of Nephrology, Beijing Boai Hospital, China Rehabilitation Research Center, Captain Medical University, Rehabilitation Medical College, Beijing, China. Department of Nephrology, Aviation General Hospital, Beijing, China. Department of Nephrology, China Academy of Chinese Medical Sciences Guang'anmen Hospital, Beijing, China. Department of Nephrology, Beijing Aerospace General Hospital, Beijing, China. Department of Nephrology, Peking University People's Hospital, Beijing, China. zuoli@bjmu.edu.cn.