Table 3.

Assesment of the risk of bias

Author, year	Random sequence generation	Allocation concealment	Blinding	Incomplete outcome data	Selective reporting	Other bias
Kanoriya D. et al., 2017 [14]	+	?	+	+	+	+
Bizzarro S. et al., 2017 [13]	+	+	+	+	+	+
Denez E.M. et al., 2016 [14]	+	–	–	+	+	+
Matesanz P. et al., 2013 [20]	+	+	+	+	+	+
Krück C. et al., 2012 [21]	–	+	–	+	+	+
Sakellari D. et al., 2010 [15]	+	+	+	+	+	+
Paolantonio M. et al., 2009 [22]	+	–	+	+	+	+
Paolantonio M. et al., 2008 [23]	+	–	+	+	+	+
Paolantonio M. et al., 2008 [24]	+	–	+	+	+	+
Cosyn J. et al., 2007 [25]	+	–	+	+	+	+
Azmak N. et al., 2002 [26]	+	–	–	+	+	+
Heasman PA. et al., 2001 [27]	–	–	–	+	+	+

+ = Low risk? = Unclear risk - = High risk