Table 2.

The summary of review authors’ judgments about each risk of bias item for included studies.

Study	Random sequence generation	Allocation concealment	Blinding	Incomplete outcome data	Selective reporting	Other bias
Serban et l. (1982) [29]	L	U	L	L	L	U
Mani et al. (2000) [27]	U	U	H	L	L	U
Parikh et al. (2001) [28]	L	U	H	L	L	L
Lee et al. (2008) [26]	L	U	H	L	L	L
Kaur et al. (2008) [25]	U	U	H	L	L	L
Anitha et al. (2010) [23]	U	U	H	L	L	U
Alam et al. (2016) [22]	L	L	L	L	L	L
Beihaghi et al. (2017) [24]	L	U	H	L	L	U

H: high risk of bias; L: low risk of bias; U: unclear or unrevealed risk of bias. Criteria defined for risk of bias assessment are according to the Cochrane guidelines.

According to Cochrane criteria, study consider as a poor quality if it had high risk of bias in ≥2 items or unclear risk of bias in ≥3 criteria.