Table 2

Risk of bias of included randomised controlled trials*

Study: first author (year)	Random sequence generation	Allocation concealment	Patient blinding	Assessor blinding	Reporting drop-out or withdrawal^†	Intention-to-treat analysis^†	Selective outcome reporting
Ni (2010)11	L	L	H	L	L	H	U
Brismee (2007)12	L	H	H	L	L	H	U
Wang (2009)13	L	L	H	L	L	L	L
Lee (2009)14	L	L	H	L	L	L	U
Song (2003)15	L	L	H	U	L	H	H
Song (2009)16	L	U	H	U	L	H	U
Fransen (2007)17	L	H	H	L	L	L	L
Hartman (2000)18	L	U	H	U	L	H	H
Adler (2007)19	L	L	H	U	L	L	U

↵* Domains of quality assessment based on Cochrane tools for assessing risk of bias.
↵† Two domains referring to ‘incomplete outcome data’ in the Cochrane tools for assessing risk of bias.
H, high risk of bias; L, low risk of bias; U, unclear (uncertain risk of bias).