Table 3.

Risk of bias.^a

Author	Selection bias		Performance bias	Detection bias	Attrition bias
	Random sequence generation	Allocation concealment	Single blind	Blinding of outcome assessor	Missing data
Beauchamp et al [27]	+	+	–	+	+
Blom et al [28]	+	+	+	+	–
Chih et al [29]	+	+	–	+	–
Cristancho-Lacroix et al [30]	+	+	–	–	–
DuBenske et al [31]	+	+	–	+	–
Eames et al [32]	+	+	–	+	+
Kim et al [33]	+	+	–	?	+
McLaughlin et al [34]	+	+	–	+	+
Namkoong et al [35]	+	+	–	+	–
Pierce et al [36]	+	+	–	?	–
Smith et al [37]	+	+	–	+	–
Torkamani et al [38]	+	+	–	?	?

^a+: low risk of bias; – high risk of bias; ?: unclear risk of bias.