Table 4.

Bias assessment

Methodological items	De Grandis, 2002	Sima UC, 2005	Sima UCE, 2005	Youle, 2007
Random sequence generation	Low risk	Uncertain risk	Uncertain risk	Low risk
Allocation concealment	Low risk	Uncertain risk	Uncertain risk	Uncertain risk
Blinding of participants and personnel	Low risk	Uncertain risk	Uncertain risk	Uncertain risk
Blinding of outcome assessment	Low risk	Uncertain risk	Uncertain risk	Uncertain risk
Incomplete outcome data	Low risk	Low risk	Low risk	Low risk
Selective reporting	Uncertain	Uncertain risk	Uncertain risk	Uncertain risk
Other bias	Low risk	Low risk	Low risk	Low risk