Table 2.

Quality assessment of included RCTs.

Study	Randomization	Blinding	Allocation concealment	Comparative baseline	>80% follow-up	Free of selective reporting
Chen et al. 2006 [14]	Mentioned	Unclear	Unclear	Yes	Yes	Yes
Wang et al. 2006 [15]	Yes	Yes	Yes	Yes	Yes	Yes
Kato et al. 2008 [16]	Yes	Unclear	Unclear	Yes	Yes	Yes
Liu et al. 2008 [17]	Mentioned	Yes	Unclear	Yes	Yes	Yes
Feng et al. 2010 [19]	Yes	Yes	Yes	Yes	Yes	Yes
Rahbari et al. 2011 [21]	Yes	Yes	Yes	Yes	Yes	Yes
Zhu et al. 2012 [22]	Yes	Yes	Yes	Yes	Yes	Yes
Ryu et al. 2010 [24]	Yes	Yes	Yes	Yes	Yes	Yes
Wang et al. 2013 [25]	Yes	Yes	Yes	Yes	Yes	Yes

Yes: the method was properly adopted and used; mentioned: the method was reported without detailed description; unclear: no relevant information was found.