Table 5. Quality assessment of RCTs.

Study	Selection			Performance		Detection		Attrition		Reporting	Other sources of bias
	Randomized method	Allocation concealment		Blinding of participants		Blinding of assessment		Incompleteness of data		Selective outcome reporting
Gralla et al., 2007	Unclear	Unclear		High risk		High risk		Low risk		Low risk	Low risk
Ahmed et al., 2011	Unclear	Unclear		High risk		High risk		Low risk		Low risk	Low risk

The quality of identified RCTs were assessed by the Cochrane risk of bias tool. RCT, randomized controlled trial.