1 Department of Pediatrics, Daqing Longnan Hospital (The Fifth Affiliated Hospital of Qiqihar Medical College), Daqing, China.
2 Department of Pediatrics, Daqing Oilfield General Hospital, Daqing, China.
3 Department of Pediatrics, Daqing Longnan Hospital (The Fifth Affiliated Hospital of Qiqihar Medical College), Daqing, China - yangguangze@petrochina.com.cn.