Table 2.

Quality of the included studies.

Study	Random allocation method	Allocation concealment	Blind method	Completion of the outcome data	Selective report of outcome	Other bias resources
Shuzhen et al. (2009)	Unclear	Unclear	Unclear	100% completed	Unclear	No
Xingrui et al. (2011)	Unclear	Unclear	Unclear	100% completed	Unclear	No
Xiao et al. (2012)	Unclear	Unclear	Unclear	100% completed	No	No
Wei et al. (2012)	Unclear	Unclear	Unclear	100% completed	No	No
Wenhan and Xiangfu (2013)	Unclear	Unclear	Unclear	100% completed	No	No
Yuyan and Xingcheng (2015)	Unclear	Unclear	Unclear	100% completed	Unclear	No