Table 3.

Risk of bias

Study	Random sequence generation	Allocation concealment	Blinding of outcome assessment	Incomplete outcome data
Alvarez et al. 2016 [12]	Low	High	Low	High
Belli et al. 2011 [28]	Low	High	High	High
Kadoglou et al. 2007 [35]	Low	High	High	High
Kadoglou et al. 2012 [44]	Low	High	High	High
Lambers et al. 2008 [29]	Low	Low	Low	High
Mitranun et al. 2014 [23]	Low	High	High	High
Negri et al. 2010 [30]	Low	High	High	High
Oliveira et al. 2012 [31]	Low	High	High	High
Sentinelli et al. 2014 [32]	Low	High	High	Low
Tomar et al. 2013 [33]	Low	High	High	Low
Vancea et al. 2009 [45]	Low	High	High	Low
Yavari et al. 2012 [34]	Low	High	High	Low
Blonk et al. 1994 [36]	High	High	Unclear	High
Church et al. 2010 [20]	Low	High	Low	Low
Emereziani et al. 2015 [37]	Low	High	High	Low
Giannopoulou et al. 2005 [38]	High	High	High	High
Jorge et al. 2011 [22]	Low	High	High	Low
Karstoft et al. 2013 [21]	Low	High	Low	High
Kwon et al. 2011 [39]	Low	High	High	High
Midlebrooke et al. 2006 [40]	Low	High	High	High
Nuttamonwarakul et al. 2012 [46]	Low	High	High	Low
Parra-Sanchez et al. 2015 [41]	Low	Low	Low	High
Shenoy et al. 2009 [42]	Low	High	High	High
Yan et al. 2014 [43]	Low	High	High	Low