Study Year of
publication
Random
sequence
generation
Allocation
concealment
Blinding of
participant’s
and personnel
Blinding of
outcomes
assessment
Incomplete
outcome
data
Selective
reporting
Other bias
Hunziker et al. [1] 2012 - + + + + ? +
Sun et al. [2] 2012 - + + + + + +
Xiao et al. [6] 2016 ? + + + + + ?
Kim et al. [7] 2014 + ? ? + + + +
Mantripragada et al. [9] 2016 + ? + + + + ?
Lee et al. [12] 2014 ? ? + + + ? ?
Bouyer et al. [14] 2016 + ? ? + + + +
Jiang et al. [15] 2013 + ? ? + + + +

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