Author Random
sequence
generation 		Allocation
concealment 		Blinding Incomplete
outcome data 		Selective
reporting 		Other
bias
Heitz-Mayfield et al. [16] ? ? ? - - -
Papadopoulos et al. [17] + ? + + ? +
de Waal et al [21] + + + + - +
Romeo et al. [22] - - - + - +
Romeo et al. [23] - - - + - +
de Waal et al. [29] + + + + - +

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