Table 2.

The risk of bias of included studies

Included studies	Sequence generation	Allocation concealment	Blinding	Incomplete outcome data addressed	Free of selective outcome reporting	Free of other bias	Quality degree
WSHASG 1991	Yes	Yes	Unclear	Unclear	Yes	Yes	B
Law et al. [17]	Yes	Yes	Unclear	Yes	Yes	Yes	A
Laterza et al. [25]	Yes	Unclear	Unclear	Yes	Yes	Yes	B
Hsu et al. [33]	Yes	Unclear	Unclear	Yes	Yes	Yes	B
Luechakiettisak and Kasetsunthorn [16]	Yes	Unclear	Unclear	Yes	Yes	Yes	B
Aquino et al. [31]	Yes	Unclear	Unclear	Yes	Yes	Yes	B
Saluja et al. [35]	Yes	Yes	Unclear	Yes	Yes	Yes	A
Cai et al. [36]	Yes	Unclear	Unclear	Unclear	Unclear	Unclear	C
Yang et al. [36]	Yes	Unclear	Unclear	Unclear	Unclear	Unclear	C