Table 2.

Risk of bias assessment (N = 21).

Author and year	Randomization process	Deviation from intended intervention	Missing data	Measurement of outcome	Selective reporting of results	Overall risk
Chen et al., 2020	Low risk	Some concerns	Low risk	Low risk	Low risk	Some concerns
Chen et al., 2020	Some concerns	Some concerns	Low risk	Low risk	Low risk	High risk
Gao et al., 2012	Low risk	Some concerns	Low risk	Low risk	Low risk	Some concerns
Huang et al., 2013	Low risk	Some concerns	Low risk	Low risk	Low risk	Some concerns
Jianjun et al., 2018	Some concerns	Some concerns	Low risk	Low risk	Low risk	High risk
Jie et al., 2006	Some concerns	Some concerns	Low risk	Low risk	Low risk	High risk
Kuang et al., 2006	Low risk	Some concerns	Low risk	High risk	Low risk	High risk
Li et al., 2011	Low risk	Some concerns	Low risk	Low risk	Low risk	Some concerns
Lu et al., 2013	Low risk	Some concerns	Low risk	High risk	Low risk	High risk
Lu et al., 2018	Low risk	Some concerns	Low risk	Low risk	Low risk	Some concerns
Su et al., 2012	Low risk	Low risk	Low risk	High risk	Low risk	High risk
Tao et al., 2013	Low risk	Low risk	Low risk	Low risk	Some concerns	Some concerns
Wang et al., 2015	Low risk	Some concerns	Low risk	High risk	Low risk	High risk
Wu et al., 2014	Low risk	Some concerns	Low risk	Low risk	Low risk	Some concerns
Zeng et al., 2008	Low risk	Some concerns	Low risk	High risk	Low risk	High risk
Zhang et al., 2010	Low risk	Some concerns	Low risk	Low risk	Low risk	Some concerns
Zhang et al., 2013	Low risk	Low risk	Low risk	High risk	Low risk	High risk
Zheng et al., 2017	Low risk	Low risk	Low risk	Low risk	Some concerns	Some concerns
Zhou et al., 2014	Low risk	Some concerns	Low risk	Low risk	Low risk	Some concerns
Zhu et al., 2010	Low risk	Some concerns	Low risk	Low risk	Low risk	Some concerns
Zhu et al., 2013	Low risk	Some concerns	Low risk	High risk	Low risk	High risk