1 Department of Nephrology, Xi'an Children's Hospital, Xi'an, China.
2 Shaanxi Institute for Pediatric Diseases, Xi'an Key Laboratory of Children's Health and Diseases, Xi'an Children's Hospital, Xi'an, China.
3 School of Public Health, Xi'an Jiaotong University, Xi'an, China.
4 Shaanxi Institute for Pediatric Diseases, Xi'an Key Laboratory of Children's Health and Diseases, Xi'an Children's Hospital, Xi'an, China. sunhongligo@yeah.net.