Table 2.

Cochrane risk of bias item for each included trials

Study	Random sequence generation	Allocation concealment	Blinding of participants and personnel	Blinding of outcome assessment	Incomplete outcome data	Selective reporting	Other bias
Ou et al. 2020	L	U	H	H	L	L	L
Allen et al. 2019	H	H	H	H	L	L	L
Mikirova et al. 2019	H	H	H	H	U	L	U
Wang et al. 2019	H	H	H	H	L	L	L
Zhao et al. 2018	U	U	H	U	L	L	L
Nielsen et al. 2017	H	H	H	U	L	L	U
Polireddy et al. 2017	H	H	H	H	L	L	U
Schoenfeld et al. 2017	H	H	H	H	L	L	U
Hoffer et al. 2015	H	H	H	H	L	L	L
Kawada et al. 2014	H	H	H	H	L	L	U
Ma et al. 2014	L	U	L	H	L	L	L
Stephenson et al. 2013	H	H	H	H	L	L	L
Welsh et al. 2013	H	H	H	H	L	L	L
Mikirova et al. 2012	H	H	H	H	L	L	L
Monti et al. 2012	H	H	H	H	L	L	L
Berenson et al. 2009	H	U	H	U	L	L	U
Hoffer et al. 2008	H	U	H	U	L	L	U
Yeom et al. 2007	H	U	H	U	L	L	L
Riordan et al. 2005	H	U	H	U	L	L	L
Correa et al. 2000	L	L	L	L	L	L	L
Moertel et al. 1985	L	L	L	L	L	L	U
Poulter et al.1984	H	U	H	H	L	L	U
Murata et al. 1982	H	U	H	H	L	L	U
Creagan et al. 1979	L	L	L	L	L	L	L
Cameron et al. 1978	H	L	U	U	L	L	U
Thomsen et al. 2019	H	L	H	U	L	L	U
Springett et al. 2015	H	L	H	U	L	L	U
Nesaretnam et al. 2010	H	L	L	L	L	L	U
Lippman et al. 2009	L	L	H	U	L	L	U
McKeown-Eyssen et al. 1988	L	L	L	L	L	L	U

Legend: H: High risk of bias; L: Low risk of bias; U: Unclear or unrevealed risk of bias