Table 2.

Quality assessment of the included randomized controlled trials.

Included trials	Sequence generation	Allocation concealment	Blinding of participants personnel	Blinding of outcome assessors	Incomplete outcome data	Selective outcome reporting	Other sources of bias	Risk of bias
Cheng 2007 [14]	Unclear	Unclear	Unclear	Unclear	Unclear	No	Unclear	High
Jin 2011 [15]	Unclear	Unclear	Unclear	Unclear	Unclear	No	Unclear	High
Zhang et al. 2008 [16]	Unclear	Unclear	Unclear	Unclear	Unclear	No	Unclear	High
Lv et al. 2010 [17]	Unclear	Unclear	Double-blind method	Unclear	Yes	No	Unclear	Unclear
Dong et al. 2010 [18]	Unclear	Unclear	Unclear	Unclear	Yes	No	Unclear	High
Yan et al. 2011 [19]	Unclear	Unclear	Unclear	Unclear	No	No	Unclear	High
Zhang 2012 [20]	Unclear	Unclear	Unclear	Unclear	Unclear	No	Unclear	High
Lu et al. 2010 [21]	Unclear	Unclear	Unclear	Unclear	Yes	No	Unclear	High
Zhang et al. 2011 [22]	Odd and even numbers	Unclear	Double-blind method	Unclear	Unclear	No	Unclear	Unclear
Xie and Shen 2006 [23]	Table of random number	Unclear	Unclear	Unclear	Unclear	No	Unclear	Unclear
Xu 2008 [24]	Unclear	Unclear	Unclear	Unclear	Unclear	No	Unclear	High
Gao 2012 [25]	Unclear	Unclear	Unclear	Unclear	Unclear	No	Unclear	High
Li et al. 2008 [26]	Unclear	Unclear	Unclear	Unclear	Yes	No	Unclear	High
Zheng and Zhang 2013 [27]	Unclear	Unclear	Unclear	Unclear	Yes	No	Unclear	High