Study Year Random
sequence
generation 		Allocation
concealment 		Blinding of
participants and
personnel 		Blinding of
outcome
assessment 		Incomplete
outcome
data 		Selective
reporting
Jun et al. [15] 2014 + + + + ? ?
Jeong et al. [16] 2014 - ? + + ? ?
Kim et al. [17] 2014 - - + + + +
Kim et al. [18] 2016 + + ? ? ? -
Lee et al. [19] 2013 - - + + + -
Sohn et al. [20] 2018 - - ? ? ? ?
Xu et al. [21] 2018 - + + ? ? ?

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