Study Random
sequence
generation 		Allocation
concealment 		Blinding of
participants and
personnel 		Blinding of
outcome
assessment 		Incomplete
outcome
data 		Selective
reporting 		Other
bias
Arisan et al. [20] + - - ? + + ?
Bassetti et al. [21] + - - + + + ?
Esposito et al. [22] + - - + + + +
Hallström et al. [23] + + - - + + +
John et al. [24] + - - + + - ?
Machtei et al. [25] + + + + + + ?
Persson et al. [26] + - - ? + + ?
Riben-Grundstrom et al. [27] + + - + + - ?
Swierkot et al. [28] + - - + + + +

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