Table 2.

Risk bias assessment according to according to the Cochrane collaborations tool

Study	Random sequence generation	Allocation concealment	Blinding of participants and personnel	Blinding of outcome assessment	Incomplete outcome data
Castro et al. [41]	+	n.a	−	+	+
Sharma et al. [54]	+	n.a	−	−	+
Mourao et al. [56]	+	n.a	−	−	+
Canellas et al. [47]	+	n.a	+	+	+
Ahmed et al. [53]	−	n.a	−	−	+
Areewong et al. [55]	+	n.a	−	−	+
Ustaoglu et al. [42]	+	n.a	Participant - Personnel +	+	+
Giudice et al. [40]	+	n.a	–	+	+
Kumar et al. [43]	−	n.a	?	−	+
Asmael et al. [58]	−	n.a	−	−	−
Clark et al. [39]	+	n.a	?	+	+
Alzahrani et al. [44]	−	n.a	−	−	+
Temmerman al. [50]	+	n.a	−	−	+
Marenzi et al. [57]	+	n.a	?	?	+
Suttapreyasri et al. [45]	−	n.a	−	−	+
Hauser et al. [46]	?	n.a	−	?	+
Thakkar et al. [52]	+	n.a	−	−	+
Yewale et al. [51]	+	n.a	−	+	+

 + low ristk, −high risk, ? unclear risk, n.a., not applicable