Table 2.

Quality evaluation results of the 21 included RCTs.

Study	Random sequence generation	Allocation hiding	Blind researchers and subjects	Blind evaluation of research results	Integrity of result data	Optional reporting of research results	Other biases
Bai et al.[11]	L	U	U	U	H	L	U
Ban et al. [12]	L	U	U	U	L	L	U
Chen et al. [13]	L	U	U	U	H	L	U
Chen et al. [14]	L	U	U	U	L	L	U
Dong [15]	U	U	U	U	H	L	U
Feng [16]	U	U	U	U	L	L	U
Gao [17]	U	U	U	U	L	L	U
Geng et al. [18]	U	U	U	U	L	L	U
He [19],	U	U	U	U	L	L	U
Huang and Yuan [20]	L	U	U	U	L	L	U
Jin et al. [22]	L	U	U	U	L	L	U
Liang et al. [23]	U	U	U	U	H	L	U
Li et al. [24]	L	U	U	U	H	L	U
Li [25]	U	U	U	U	H	L	U
Li et al. [26]	U	U	U	U	L	L	U
Ma [27]	L	U	U	U	L	L	U
Pei [28]	L	U	U	U	L	L	U
Yuan [30]	L	U	U	U	L	L	U
Zhang et al. [31]	L	U	U	U	L	L	U
Zhang et al. [32]	U	U	U	U	L	L	U
Zhang [33]	U	U	U	U	H	L	U

L: low risk; U: unknown risk; H: high risk.