Table 2. Quality appraisal summary of included trials.

Authors, year	Random allocation	Allocation concealment	Blinding	Incomplete outcome	Selective reporting	Other bias	Quality level
Dunleavy et al., 2015	+	+	−	+	+	+	C
Cramer et al., 2013	+	+	−	+	+	+	C
Michalsen et al., 2012	+	+	−	+	+	+	C

+: criteria met; −: criteria were not met; ?: unclear whether criteria were met