Table 5.

Risk of bias summary according to the Cochrane risk of bias tool.

Study	Selection Bias		Performance Bias	Detection Bias	Attrition Bias	Reporting Bias	Quality
	Random Sequence Generation	Allocation Concealment	Blinding of Participants and Personnel	Blinding of Outcome Assessment	Incomplete Outcome Data Addressed	Selective Reporting
Boers et al. [13]	+	−	−	+	+	+	Good
Fontes-Villalba et al. [16] a	+	−	−	+	+	+	Good
Jönsson et al. [9] a	+	−	−	+	+	+	Good
Lindeberg et al. [17]	+	−	−	+	?	+	Good
Masharani et al. [18]	?	−	−	−	+	+	Fair

^a Studies conducted on the same population; + low risk; ? unclear risk; − high risk.