Study Year of
publication 		Random
sequence
generation 		Allocation
concealment 		Blinding of
outcome
assessment 		Incomplete
outcome
data 		Selective
reporting 		Other
sources of
bias
Boynuegri et al. [21] 2012 ? ? ? + + +
Chung et al. [22] 2006 ? ? + + + +
Adibrad et al. [23] 2009 ? ? + + + +
Bouri et al. [24] 2008 + ? + + + +
Romanos et al. [25] 2015 ? ? + + + +
Souza et al. [26] 2015 + + + + + +
Kim et al. [31] 2009 ? ? ? + + +
Esper et al. [32] 2012 ? ? ? + + +

+ = low risk; ? = unclear risk; - = high risk.