TABLE 3.

Risk of bias.

References	A	B	C	D	E	F	G
Ai et al. (2020)	L	U	U	U	L	U	U
Ding et al. (2020)	L	U	U	U	L	U	U
Duan et al. (2020)	L	U	U	U	L	U	U
Fu et al. (2020a)	L	U	U	U	L	U	U
Fu et al. (2020b)	L	U	U	U	L	U	U
Hu et al. (2020)	L	U	U	U	L	U	U
Hu et al. (2020)	L	U	U	L	L	U	U
Yu et al. (2020)	L	U	U	U	L	U	U
Zhang et al. (2020)	U	U	U	U	L	U	U

A, random sequence generation (selection bias); B, allocation concealment (selection bias); C, blinding of participants and personnel (performance bias); D, blinding of outcome assessment (detection bias); E, incomplete outcome data (attrition bias); F, selective reporting (reporting bias); G, other biases; L, low risk; H, high risk; U, unclear.