Table 2.

The risk of bias of included RCTs and cluster RCTs

Studies	Year	Selection bias		Performance bias	Detection bias	Attrition bias	Reporting bias	Other bias
		Random sequence generation	Allocation concealment	Blinding of participants and personnel	Blinding of outcome assessment	Incomplete outcome data	Selective reporting	Anything else, ideally prespecified
Cals et al20	2009	H	H	H	U	L	L	U
Cals et al13	2010	U	U	H	U	L	L	U
Cals et al19	2011	H	H	H	U	L	L	U
Cals et al21	2013	H	H	H	U	L	L	U
Diederichsen et al25	2000	U	U	H	U	U	L	U
Gonzales et al11	2011	L	L	H	U	L	L	U
Melbye et al26	1995	U	U	H	U	U	L	U

H = high risk of bias. L = low risk of bias. U = unclear risk of bias.