Ethics statements
This study was approved by the Ethics Committee of Guangdong Provincial People’s Hospital (No. [2011] 28, Full names of the Ethics committees are: Jinrui Ou, Jianxing Cui, Nianqiao Zhang, Jianwei Mo, Deying Qian, Jimei Chen, Feizhou Jiang, Zuoyue Liu, Peihua Zheng, You Huang). All patients provided written informed consent prior to participating in the study.