Table 2.

Risk of bias of included studies.

Studies	Random sequence generation (selection bias)	Allocation concealment (selection bias)	Blinding of participants and personnel (performance bias)	Blinding of outcome assessment (detection bias)	Incomplete outcome data (attrition bias)	Selective reporting (reporting bias)	Other bias
Abd-Elgawad et al	Low risk	Low risk	Low risk	Low risk	Low risk	Low risk	Low risk
Ferreira et al.	Low risk	Unclear risk	Low risk	Low risk	Low risk	Low risk	Low risk
Sharma et al.	Low risk	Low risk	High risk	High risk	Low risk	Low risk	Unclear risk
Zhang et al.	Low risk	Low risk	Low risk	Unclear risk	Low risk	Low risk	Unclear risk
Glass et al.	Low risk	Unclear risk	High risk	High risk	Low risk	Low risk	Unclear risk
Romano-Keeler et al.	High risk	High risk	High risk	High risk	Low risk	Low risk	Unclear risk
Sohn et al.	Unclear risk	Low risk	High risk	High risk	Low risk	Low risk	Unclear risk
Lee et al.	Low risk	Low risk	Low risk	Low risk	Low risk	Low risk	Low risk
Rodriguez et al.	Unclear risk	Unclear risk	Unclear risk	Unclear risk	Low risk	Low risk	Unclear risk