Table 2.

Summary of risk of bias assessment for studies included.

Study	Random sequence generation	Allocation concealment	Blinding of participants and personnel	Blinding of outcome assessment or statistician	Complete outcome data	Selective reporting	Other sources of bias
Dong et al. 2014 [16]	+	?	?	?	+	+	?
Ren 2013 [17]	+	+	?	?	+	+	?
Zhang et al. 2011 [18]	?	?	?	?	+	+	?
Huang 2011 [19]	?	?	?	?	+	+	?
Li and Yan 2015 [20]	?	?	?	?	+	+	?
Huang and Si 2015 [21]	?	?	?	?	+	+	?
Wen 2013 [22]	+	?	?	+	+	+	?
Bai 2013 [23]	+	+	+	+	+	+	?
Zhu and Fei 2011 [24]	+	?	?	?	+	+	?
Ji et al. 2011 [25]	+	?	?	?	+	+	?

“+” = low risk of bias; “?” = unclear risk of bias.